graph.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "graph.h"
   4 #include "diff.h"
   5 #include "revision.h"
   6
   7 /*
   8  * TODO:
   9  * - Add colors to the graph.
  10  *   Pick a color for each column, and print all characters
  11  *   in that column with the specified color.
  12  *
  13  * - Limit the number of columns, similar to the way gitk does.
  14  *   If we reach more than a specified number of columns, omit
  15  *   sections of some columns.
  16  *
  17  * - The output during the GRAPH_PRE_COMMIT and GRAPH_COLLAPSING states
  18  *   could be made more compact by printing horizontal lines, instead of
  19  *   long diagonal lines.  For example, during collapsing, something like
  20  *   this:          instead of this:
  21  *   | | | | |      | | | | |
  22  *   | |_|_|/       | | | |/
  23  *   |/| | |        | | |/|
  24  *   | | | |        | |/| |
  25  *                  |/| | |
  26  *                  | | | |
  27  *
  28  *   If there are several parallel diagonal lines, they will need to be
  29  *   replaced with horizontal lines on subsequent rows.
  30  */
  31
  32 struct column {
  33         /*
  34          * The parent commit of this column.
  35          */
  36         struct commit *commit;
  37         /*
  38          * XXX: Once we add support for colors, struct column could also
  39          * contain the color of its branch line.
  40          */
  41 };
  42
  43 enum graph_state {
  44         GRAPH_PADDING,
  45         GRAPH_SKIP,
  46         GRAPH_PRE_COMMIT,
  47         GRAPH_COMMIT,
  48         GRAPH_POST_MERGE,
  49         GRAPH_COLLAPSING
  50 };
  51
  52 struct git_graph {
  53         /*
  54          * The commit currently being processed
  55          */
  56         struct commit *commit;
  57         /* The rev-info used for the current traversal */
  58         struct rev_info *revs;
  59         /*
  60          * The number of interesting parents that this commit has.
  61          *
  62          * Note that this is not the same as the actual number of parents.
  63          * This count excludes parents that won't be printed in the graph
  64          * output, as determined by graph_is_interesting().
  65          */
  66         int num_parents;
  67         /*
  68          * The width of the graph output for this commit.
  69          * All rows for this commit are padded to this width, so that
  70          * messages printed after the graph output are aligned.
  71          */
  72         int width;
  73         /*
  74          * The next expansion row to print
  75          * when state is GRAPH_PRE_COMMIT
  76          */
  77         int expansion_row;
  78         /*
  79          * The current output state.
  80          * This tells us what kind of line graph_next_line() should output.
  81          */
  82         enum graph_state state;
  83         /*
  84          * The output state for the previous line of output.
  85          * This is primarily used to determine how the first merge line
  86          * should appear, based on the last line of the previous commit.
  87          */
  88         enum graph_state prev_state;
  89         /*
  90          * The index of the column that refers to this commit.
  91          *
  92          * If none of the incoming columns refer to this commit,
  93          * this will be equal to num_columns.
  94          */
  95         int commit_index;
  96         /*
  97          * The commit_index for the previously displayed commit.
  98          *
  99          * This is used to determine how the first line of a merge
 100          * graph output should appear, based on the last line of the
 101          * previous commit.
 102          */
 103         int prev_commit_index;
 104         /*
 105          * The maximum number of columns that can be stored in the columns
 106          * and new_columns arrays.  This is also half the number of entries
 107          * that can be stored in the mapping and new_mapping arrays.
 108          */
 109         int column_capacity;
 110         /*
 111          * The number of columns (also called "branch lines" in some places)
 112          */
 113         int num_columns;
 114         /*
 115          * The number of columns in the new_columns array
 116          */
 117         int num_new_columns;
 118         /*
 119          * The number of entries in the mapping array
 120          */
 121         int mapping_size;
 122         /*
 123          * The column state before we output the current commit.
 124          */
 125         struct column *columns;
 126         /*
 127          * The new column state after we output the current commit.
 128          * Only valid when state is GRAPH_COLLAPSING.
 129          */
 130         struct column *new_columns;
 131         /*
 132          * An array that tracks the current state of each
 133          * character in the output line during state GRAPH_COLLAPSING.
 134          * Each entry is -1 if this character is empty, or a non-negative
 135          * integer if the character contains a branch line.  The value of
 136          * the integer indicates the target position for this branch line.
 137          * (I.e., this array maps the current column positions to their
 138          * desired positions.)
 139          *
 140          * The maximum capacity of this array is always
 141          * sizeof(int) * 2 * column_capacity.
 142          */
 143         int *mapping;
 144         /*
 145          * A temporary array for computing the next mapping state
 146          * while we are outputting a mapping line.  This is stored as part
 147          * of the git_graph simply so we don't have to allocate a new
 148          * temporary array each time we have to output a collapsing line.
 149          */
 150         int *new_mapping;
 151 };
 152
 153 struct git_graph *graph_init(struct rev_info *opt)
 154 {
 155         struct git_graph *graph = xmalloc(sizeof(struct git_graph));
 156         graph->commit = NULL;
 157         graph->revs = opt;
 158         graph->num_parents = 0;
 159         graph->expansion_row = 0;
 160         graph->state = GRAPH_PADDING;
 161         graph->prev_state = GRAPH_PADDING;
 162         graph->commit_index = 0;
 163         graph->prev_commit_index = 0;
 164         graph->num_columns = 0;
 165         graph->num_new_columns = 0;
 166         graph->mapping_size = 0;
 167
 168         /*
 169          * Allocate a reasonably large default number of columns
 170          * We'll automatically grow columns later if we need more room.
 171          */
 172         graph->column_capacity = 30;
 173         graph->columns = xmalloc(sizeof(struct column) *
 174                                  graph->column_capacity);
 175         graph->new_columns = xmalloc(sizeof(struct column) *
 176                                      graph->column_capacity);
 177         graph->mapping = xmalloc(sizeof(int) * 2 * graph->column_capacity);
 178         graph->new_mapping = xmalloc(sizeof(int) * 2 * graph->column_capacity);
 179
 180         return graph;
 181 }
 182
 183 void graph_release(struct git_graph *graph)
 184 {
 185         free(graph->columns);
 186         free(graph->new_columns);
 187         free(graph->mapping);
 188         free(graph);
 189 }
 190
 191 static void graph_update_state(struct git_graph *graph, enum graph_state s)
 192 {
 193         graph->prev_state = graph->state;
 194         graph->state = s;
 195 }
 196
 197 static void graph_ensure_capacity(struct git_graph *graph, int num_columns)
 198 {
 199         if (graph->column_capacity >= num_columns)
 200                 return;
 201
 202         do {
 203                 graph->column_capacity *= 2;
 204         } while (graph->column_capacity < num_columns);
 205
 206         graph->columns = xrealloc(graph->columns,
 207                                   sizeof(struct column) *
 208                                   graph->column_capacity);
 209         graph->new_columns = xrealloc(graph->new_columns,
 210                                       sizeof(struct column) *
 211                                       graph->column_capacity);
 212         graph->mapping = xrealloc(graph->mapping,
 213                                   sizeof(int) * 2 * graph->column_capacity);
 214         graph->new_mapping = xrealloc(graph->new_mapping,
 215                                       sizeof(int) * 2 * graph->column_capacity);
 216 }
 217
 218 /*
 219  * Returns 1 if the commit will be printed in the graph output,
 220  * and 0 otherwise.
 221  */
 222 static int graph_is_interesting(struct git_graph *graph, struct commit *commit)
 223 {
 224         /*
 225          * If revs->boundary is set, commits whose children have
 226          * been shown are always interesting, even if they have the
 227          * UNINTERESTING or TREESAME flags set.
 228          */
 229         if (graph->revs && graph->revs->boundary) {
 230                 if (commit->object.flags & CHILD_SHOWN)
 231                         return 1;
 232         }
 233
 234         /*
 235          * Uninteresting and pruned commits won't be printed
 236          */
 237         return (commit->object.flags & (UNINTERESTING | TREESAME)) ? 0 : 1;
 238 }
 239
 240 static struct commit_list *next_interesting_parent(struct git_graph *graph,
 241                                                    struct commit_list *orig)
 242 {
 243         struct commit_list *list;
 244
 245         /*
 246          * If revs->first_parent_only is set, only the first
 247          * parent is interesting.  None of the others are.
 248          */
 249         if (graph->revs->first_parent_only)
 250                 return NULL;
 251
 252         /*
 253          * Return the next interesting commit after orig
 254          */
 255         for (list = orig->next; list; list = list->next) {
 256                 if (graph_is_interesting(graph, list->item))
 257                         return list;
 258         }
 259
 260         return NULL;
 261 }
 262
 263 static struct commit_list *first_interesting_parent(struct git_graph *graph)
 264 {
 265         struct commit_list *parents = graph->commit->parents;
 266
 267         /*
 268          * If this commit has no parents, ignore it
 269          */
 270         if (!parents)
 271                 return NULL;
 272
 273         /*
 274          * If the first parent is interesting, return it
 275          */
 276         if (graph_is_interesting(graph, parents->item))
 277                 return parents;
 278
 279         /*
 280          * Otherwise, call next_interesting_parent() to get
 281          * the next interesting parent
 282          */
 283         return next_interesting_parent(graph, parents);
 284 }
 285
 286 static void graph_insert_into_new_columns(struct git_graph *graph,
 287                                           struct commit *commit,
 288                                           int *mapping_index)
 289 {
 290         int i;
 291
 292         /*
 293          * If the commit is already in the new_columns list, we don't need to
 294          * add it.  Just update the mapping correctly.
 295          */
 296         for (i = 0; i < graph->num_new_columns; i++) {
 297                 if (graph->new_columns[i].commit == commit) {
 298                         graph->mapping[*mapping_index] = i;
 299                         *mapping_index += 2;
 300                         return;
 301                 }
 302         }
 303
 304         /*
 305          * This commit isn't already in new_columns.  Add it.
 306          */
 307         graph->new_columns[graph->num_new_columns].commit = commit;
 308         graph->mapping[*mapping_index] = graph->num_new_columns;
 309         *mapping_index += 2;
 310         graph->num_new_columns++;
 311 }
 312
 313 static void graph_update_width(struct git_graph *graph,
 314                                int is_commit_in_existing_columns)
 315 {
 316         /*
 317          * Compute the width needed to display the graph for this commit.
 318          * This is the maximum width needed for any row.  All other rows
 319          * will be padded to this width.
 320          *
 321          * Compute the number of columns in the widest row:
 322          * Count each existing column (graph->num_columns), and each new
 323          * column added by this commit.
 324          */
 325         int max_cols = graph->num_columns + graph->num_parents;
 326
 327         /*
 328          * Even if the current commit has no parents to be printed, it
 329          * still takes up a column for itself.
 330          */
 331         if (graph->num_parents < 1)
 332                 max_cols++;
 333
 334         /*
 335          * We added a column for the the current commit as part of
 336          * graph->num_parents.  If the current commit was already in
 337          * graph->columns, then we have double counted it.
 338          */
 339         if (is_commit_in_existing_columns)
 340                 max_cols--;
 341
 342         /*
 343          * Each column takes up 2 spaces
 344          */
 345         graph->width = max_cols * 2;
 346 }
 347
 348 static void graph_update_columns(struct git_graph *graph)
 349 {
 350         struct commit_list *parent;
 351         struct column *tmp_columns;
 352         int max_new_columns;
 353         int mapping_idx;
 354         int i, seen_this, is_commit_in_columns;
 355
 356         /*
 357          * Swap graph->columns with graph->new_columns
 358          * graph->columns contains the state for the previous commit,
 359          * and new_columns now contains the state for our commit.
 360          *
 361          * We'll re-use the old columns array as storage to compute the new
 362          * columns list for the commit after this one.
 363          */
 364         tmp_columns = graph->columns;
 365         graph->columns = graph->new_columns;
 366         graph->num_columns = graph->num_new_columns;
 367
 368         graph->new_columns = tmp_columns;
 369         graph->num_new_columns = 0;
 370
 371         /*
 372          * Now update new_columns and mapping with the information for the
 373          * commit after this one.
 374          *
 375          * First, make sure we have enough room.  At most, there will
 376          * be graph->num_columns + graph->num_parents columns for the next
 377          * commit.
 378          */
 379         max_new_columns = graph->num_columns + graph->num_parents;
 380         graph_ensure_capacity(graph, max_new_columns);
 381
 382         /*
 383          * Clear out graph->mapping
 384          */
 385         graph->mapping_size = 2 * max_new_columns;
 386         for (i = 0; i < graph->mapping_size; i++)
 387                 graph->mapping[i] = -1;
 388
 389         /*
 390          * Populate graph->new_columns and graph->mapping
 391          *
 392          * Some of the parents of this commit may already be in
 393          * graph->columns.  If so, graph->new_columns should only contain a
 394          * single entry for each such commit.  graph->mapping should
 395          * contain information about where each current branch line is
 396          * supposed to end up after the collapsing is performed.
 397          */
 398         seen_this = 0;
 399         mapping_idx = 0;
 400         is_commit_in_columns = 1;
 401         for (i = 0; i <= graph->num_columns; i++) {
 402                 struct commit *col_commit;
 403                 if (i == graph->num_columns) {
 404                         if (seen_this)
 405                                 break;
 406                         is_commit_in_columns = 0;
 407                         col_commit = graph->commit;
 408                 } else {
 409                         col_commit = graph->columns[i].commit;
 410                 }
 411
 412                 if (col_commit == graph->commit) {
 413                         int old_mapping_idx = mapping_idx;
 414                         seen_this = 1;
 415                         graph->commit_index = i;
 416                         for (parent = first_interesting_parent(graph);
 417                              parent;
 418                              parent = next_interesting_parent(graph, parent)) {
 419                                 graph_insert_into_new_columns(graph,
 420                                                               parent->item,
 421                                                               &mapping_idx);
 422                         }
 423                         /*
 424                          * We always need to increment mapping_idx by at
 425                          * least 2, even if it has no interesting parents.
 426                          * The current commit always takes up at least 2
 427                          * spaces.
 428                          */
 429                         if (mapping_idx == old_mapping_idx)
 430                                 mapping_idx += 2;
 431                 } else {
 432                         graph_insert_into_new_columns(graph, col_commit,
 433                                                       &mapping_idx);
 434                 }
 435         }
 436
 437         /*
 438          * Shrink mapping_size to be the minimum necessary
 439          */
 440         while (graph->mapping_size > 1 &&
 441                graph->mapping[graph->mapping_size - 1] < 0)
 442                 graph->mapping_size--;
 443
 444         /*
 445          * Compute graph->width for this commit
 446          */
 447         graph_update_width(graph, is_commit_in_columns);
 448 }
 449
 450 void graph_update(struct git_graph *graph, struct commit *commit)
 451 {
 452         struct commit_list *parent;
 453
 454         /*
 455          * Set the new commit
 456          */
 457         graph->commit = commit;
 458
 459         /*
 460          * Count how many interesting parents this commit has
 461          */
 462         graph->num_parents = 0;
 463         for (parent = first_interesting_parent(graph);
 464              parent;
 465              parent = next_interesting_parent(graph, parent))
 466         {
 467                 graph->num_parents++;
 468         }
 469
 470         /*
 471          * Store the old commit_index in prev_commit_index.
 472          * graph_update_columns() will update graph->commit_index for this
 473          * commit.
 474          */
 475         graph->prev_commit_index = graph->commit_index;
 476
 477         /*
 478          * Call graph_update_columns() to update
 479          * columns, new_columns, and mapping.
 480          */
 481         graph_update_columns(graph);
 482
 483         graph->expansion_row = 0;
 484
 485         /*
 486          * Update graph->state.
 487          * Note that we don't call graph_update_state() here, since
 488          * we don't want to update graph->prev_state.  No line for
 489          * graph->state was ever printed.
 490          *
 491          * If the previous commit didn't get to the GRAPH_PADDING state,
 492          * it never finished its output.  Goto GRAPH_SKIP, to print out
 493          * a line to indicate that portion of the graph is missing.
 494          *
 495          * If there are 3 or more parents, we may need to print extra rows
 496          * before the commit, to expand the branch lines around it and make
 497          * room for it.  We need to do this only if there is a branch row
 498          * (or more) to the right of this commit.
 499          *
 500          * If there are less than 3 parents, we can immediately print the
 501          * commit line.
 502          */
 503         if (graph->state != GRAPH_PADDING)
 504                 graph->state = GRAPH_SKIP;
 505         else if (graph->num_parents >= 3 &&
 506                  graph->commit_index < (graph->num_columns - 1))
 507                 graph->state = GRAPH_PRE_COMMIT;
 508         else
 509                 graph->state = GRAPH_COMMIT;
 510 }
 511
 512 static int graph_is_mapping_correct(struct git_graph *graph)
 513 {
 514         int i;
 515
 516         /*
 517          * The mapping is up to date if each entry is at its target,
 518          * or is 1 greater than its target.
 519          * (If it is 1 greater than the target, '/' will be printed, so it
 520          * will look correct on the next row.)
 521          */
 522         for (i = 0; i < graph->mapping_size; i++) {
 523                 int target = graph->mapping[i];
 524                 if (target < 0)
 525                         continue;
 526                 if (target == (i / 2))
 527                         continue;
 528                 return 0;
 529         }
 530
 531         return 1;
 532 }
 533
 534 static void graph_pad_horizontally(struct git_graph *graph, struct strbuf *sb)
 535 {
 536         /*
 537          * Add additional spaces to the end of the strbuf, so that all
 538          * lines for a particular commit have the same width.
 539          *
 540          * This way, fields printed to the right of the graph will remain
 541          * aligned for the entire commit.
 542          */
 543         int extra;
 544         if (sb->len >= graph->width)
 545                 return;
 546
 547         extra = graph->width - sb->len;
 548         strbuf_addf(sb, "%*s", (int) extra, "");
 549 }
 550
 551 static void graph_output_padding_line(struct git_graph *graph,
 552                                       struct strbuf *sb)
 553 {
 554         int i;
 555
 556         /*
 557          * We could conceivable be called with a NULL commit
 558          * if our caller has a bug, and invokes graph_next_line()
 559          * immediately after graph_init(), without first calling
 560          * graph_update().  Return without outputting anything in this
 561          * case.
 562          */
 563         if (!graph->commit)
 564                 return;
 565
 566         /*
 567          * Output a padding row, that leaves all branch lines unchanged
 568          */
 569         for (i = 0; i < graph->num_new_columns; i++) {
 570                 strbuf_addstr(sb, "| ");
 571         }
 572
 573         graph_pad_horizontally(graph, sb);
 574 }
 575
 576 static void graph_output_skip_line(struct git_graph *graph, struct strbuf *sb)
 577 {
 578         /*
 579          * Output an ellipsis to indicate that a portion
 580          * of the graph is missing.
 581          */
 582         strbuf_addstr(sb, "...");
 583         graph_pad_horizontally(graph, sb);
 584
 585         if (graph->num_parents >= 3 &&
 586             graph->commit_index < (graph->num_columns - 1))
 587                 graph_update_state(graph, GRAPH_PRE_COMMIT);
 588         else
 589                 graph_update_state(graph, GRAPH_COMMIT);
 590 }
 591
 592 static void graph_output_pre_commit_line(struct git_graph *graph,
 593                                          struct strbuf *sb)
 594 {
 595         int num_expansion_rows;
 596         int i, seen_this;
 597
 598         /*
 599          * This function formats a row that increases the space around a commit
 600          * with multiple parents, to make room for it.  It should only be
 601          * called when there are 3 or more parents.
 602          *
 603          * We need 2 extra rows for every parent over 2.
 604          */
 605         assert(graph->num_parents >= 3);
 606         num_expansion_rows = (graph->num_parents - 2) * 2;
 607
 608         /*
 609          * graph->expansion_row tracks the current expansion row we are on.
 610          * It should be in the range [0, num_expansion_rows - 1]
 611          */
 612         assert(0 <= graph->expansion_row &&
 613                graph->expansion_row < num_expansion_rows);
 614
 615         /*
 616          * Output the row
 617          */
 618         seen_this = 0;
 619         for (i = 0; i < graph->num_columns; i++) {
 620                 struct column *col = &graph->columns[i];
 621                 if (col->commit == graph->commit) {
 622                         seen_this = 1;
 623                         strbuf_addf(sb, "| %*s", graph->expansion_row, "");
 624                 } else if (seen_this && (graph->expansion_row == 0)) {
 625                         /*
 626                          * This is the first line of the pre-commit output.
 627                          * If the previous commit was a merge commit and
 628                          * ended in the GRAPH_POST_MERGE state, all branch
 629                          * lines after graph->prev_commit_index were
 630                          * printed as "\" on the previous line.  Continue
 631                          * to print them as "\" on this line.  Otherwise,
 632                          * print the branch lines as "|".
 633                          */
 634                         if (graph->prev_state == GRAPH_POST_MERGE &&
 635                             graph->prev_commit_index < i)
 636                                 strbuf_addstr(sb, "\\ ");
 637                         else
 638                                 strbuf_addstr(sb, "| ");
 639                 } else if (seen_this && (graph->expansion_row > 0)) {
 640                         strbuf_addstr(sb, "\\ ");
 641                 } else {
 642                         strbuf_addstr(sb, "| ");
 643                 }
 644         }
 645
 646         graph_pad_horizontally(graph, sb);
 647
 648         /*
 649          * Increment graph->expansion_row,
 650          * and move to state GRAPH_COMMIT if necessary
 651          */
 652         graph->expansion_row++;
 653         if (graph->expansion_row >= num_expansion_rows)
 654                 graph_update_state(graph, GRAPH_COMMIT);
 655 }
 656
 657 static void graph_output_commit_char(struct git_graph *graph, struct strbuf *sb)
 658 {
 659         /*
 660          * For boundary commits, print 'o'
 661          * (We should only see boundary commits when revs->boundary is set.)
 662          */
 663         if (graph->commit->object.flags & BOUNDARY) {
 664                 assert(graph->revs->boundary);
 665                 strbuf_addch(sb, 'o');
 666                 return;
 667         }
 668
 669         /*
 670          * If revs->left_right is set, print '<' for commits that
 671          * come from the left side, and '>' for commits from the right
 672          * side.
 673          */
 674         if (graph->revs && graph->revs->left_right) {
 675                 if (graph->commit->object.flags & SYMMETRIC_LEFT)
 676                         strbuf_addch(sb, '<');
 677                 else
 678                         strbuf_addch(sb, '>');
 679                 return;
 680         }
 681
 682         /*
 683          * Print '*' in all other cases
 684          */
 685         strbuf_addch(sb, '*');
 686 }
 687
 688 void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
 689 {
 690         int seen_this = 0;
 691         int i, j;
 692
 693         /*
 694          * Output the row containing this commit
 695          * Iterate up to and including graph->num_columns,
 696          * since the current commit may not be in any of the existing
 697          * columns.  (This happens when the current commit doesn't have any
 698          * children that we have already processed.)
 699          */
 700         seen_this = 0;
 701         for (i = 0; i <= graph->num_columns; i++) {
 702                 struct commit *col_commit;
 703                 if (i == graph->num_columns) {
 704                         if (seen_this)
 705                                 break;
 706                         col_commit = graph->commit;
 707                 } else {
 708                         col_commit = graph->columns[i].commit;
 709                 }
 710
 711                 if (col_commit == graph->commit) {
 712                         seen_this = 1;
 713                         graph_output_commit_char(graph, sb);
 714
 715                         if (graph->num_parents < 3)
 716                                 strbuf_addch(sb, ' ');
 717                         else {
 718                                 int num_dashes =
 719                                         ((graph->num_parents - 2) * 2) - 1;
 720                                 for (j = 0; j < num_dashes; j++)
 721                                         strbuf_addch(sb, '-');
 722                                 strbuf_addstr(sb, ". ");
 723                         }
 724                 } else if (seen_this && (graph->num_parents > 2)) {
 725                         strbuf_addstr(sb, "\\ ");
 726                 } else if (seen_this && (graph->num_parents == 2)) {
 727                         /*
 728                          * This is a 2-way merge commit.
 729                          * There is no GRAPH_PRE_COMMIT stage for 2-way
 730                          * merges, so this is the first line of output
 731                          * for this commit.  Check to see what the previous
 732                          * line of output was.
 733                          *
 734                          * If it was GRAPH_POST_MERGE, the branch line
 735                          * coming into this commit may have been '\',
 736                          * and not '|' or '/'.  If so, output the branch
 737                          * line as '\' on this line, instead of '|'.  This
 738                          * makes the output look nicer.
 739                          */
 740                         if (graph->prev_state == GRAPH_POST_MERGE &&
 741                             graph->prev_commit_index < i)
 742                                 strbuf_addstr(sb, "\\ ");
 743                         else
 744                                 strbuf_addstr(sb, "| ");
 745                 } else {
 746                         strbuf_addstr(sb, "| ");
 747                 }
 748         }
 749
 750         graph_pad_horizontally(graph, sb);
 751
 752         /*
 753          * Update graph->state
 754          */
 755         if (graph->num_parents > 1)
 756                 graph_update_state(graph, GRAPH_POST_MERGE);
 757         else if (graph_is_mapping_correct(graph))
 758                 graph_update_state(graph, GRAPH_PADDING);
 759         else
 760                 graph_update_state(graph, GRAPH_COLLAPSING);
 761 }
 762
 763 void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)
 764 {
 765         int seen_this = 0;
 766         int i, j;
 767
 768         /*
 769          * Output the post-merge row
 770          */
 771         for (i = 0; i <= graph->num_columns; i++) {
 772                 struct commit *col_commit;
 773                 if (i == graph->num_columns) {
 774                         if (seen_this)
 775                                 break;
 776                         col_commit = graph->commit;
 777                 } else {
 778                         col_commit = graph->columns[i].commit;
 779                 }
 780
 781                 if (col_commit == graph->commit) {
 782                         seen_this = 1;
 783                         strbuf_addch(sb, '|');
 784                         for (j = 0; j < graph->num_parents - 1; j++)
 785                                 strbuf_addstr(sb, "\\ ");
 786                 } else if (seen_this) {
 787                         strbuf_addstr(sb, "\\ ");
 788                 } else {
 789                         strbuf_addstr(sb, "| ");
 790                 }
 791         }
 792
 793         graph_pad_horizontally(graph, sb);
 794
 795         /*
 796          * Update graph->state
 797          */
 798         if (graph_is_mapping_correct(graph))
 799                 graph_update_state(graph, GRAPH_PADDING);
 800         else
 801                 graph_update_state(graph, GRAPH_COLLAPSING);
 802 }
 803
 804 void graph_output_collapsing_line(struct git_graph *graph, struct strbuf *sb)
 805 {
 806         int i;
 807         int *tmp_mapping;
 808
 809         /*
 810          * Clear out the new_mapping array
 811          */
 812         for (i = 0; i < graph->mapping_size; i++)
 813                 graph->new_mapping[i] = -1;
 814
 815         for (i = 0; i < graph->mapping_size; i++) {
 816                 int target = graph->mapping[i];
 817                 if (target < 0)
 818                         continue;
 819
 820                 /*
 821                  * Since update_columns() always inserts the leftmost
 822                  * column first, each branch's target location should
 823                  * always be either its current location or to the left of
 824                  * its current location.
 825                  *
 826                  * We never have to move branches to the right.  This makes
 827                  * the graph much more legible, since whenever branches
 828                  * cross, only one is moving directions.
 829                  */
 830                 assert(target * 2 <= i);
 831
 832                 if (target * 2 == i) {
 833                         /*
 834                          * This column is already in the
 835                          * correct place
 836                          */
 837                         assert(graph->new_mapping[i] == -1);
 838                         graph->new_mapping[i] = target;
 839                 } else if (graph->new_mapping[i - 1] < 0) {
 840                         /*
 841                          * Nothing is to the left.
 842                          * Move to the left by one
 843                          */
 844                         graph->new_mapping[i - 1] = target;
 845                 } else if (graph->new_mapping[i - 1] == target) {
 846                         /*
 847                          * There is a branch line to our left
 848                          * already, and it is our target.  We
 849                          * combine with this line, since we share
 850                          * the same parent commit.
 851                          *
 852                          * We don't have to add anything to the
 853                          * output or new_mapping, since the
 854                          * existing branch line has already taken
 855                          * care of it.
 856                          */
 857                 } else {
 858                         /*
 859                          * There is a branch line to our left,
 860                          * but it isn't our target.  We need to
 861                          * cross over it.
 862                          *
 863                          * The space just to the left of this
 864                          * branch should always be empty.
 865                          */
 866                         assert(graph->new_mapping[i - 1] > target);
 867                         assert(graph->new_mapping[i - 2] < 0);
 868                         graph->new_mapping[i - 2] = target;
 869                 }
 870         }
 871
 872         /*
 873          * The new mapping may be 1 smaller than the old mapping
 874          */
 875         if (graph->new_mapping[graph->mapping_size - 1] < 0)
 876                 graph->mapping_size--;
 877
 878         /*
 879          * Output out a line based on the new mapping info
 880          */
 881         for (i = 0; i < graph->mapping_size; i++) {
 882                 int target = graph->new_mapping[i];
 883                 if (target < 0)
 884                         strbuf_addch(sb, ' ');
 885                 else if (target * 2 == i)
 886                         strbuf_addch(sb, '|');
 887                 else
 888                         strbuf_addch(sb, '/');
 889         }
 890
 891         graph_pad_horizontally(graph, sb);
 892
 893         /*
 894          * Swap mapping and new_mapping
 895          */
 896         tmp_mapping = graph->mapping;
 897         graph->mapping = graph->new_mapping;
 898         graph->new_mapping = tmp_mapping;
 899
 900         /*
 901          * If graph->mapping indicates that all of the branch lines
 902          * are already in the correct positions, we are done.
 903          * Otherwise, we need to collapse some branch lines together.
 904          */
 905         if (graph_is_mapping_correct(graph))
 906                 graph_update_state(graph, GRAPH_PADDING);
 907 }
 908
 909 int graph_next_line(struct git_graph *graph, struct strbuf *sb)
 910 {
 911         switch (graph->state) {
 912         case GRAPH_PADDING:
 913                 graph_output_padding_line(graph, sb);
 914                 return 0;
 915         case GRAPH_SKIP:
 916                 graph_output_skip_line(graph, sb);
 917                 return 0;
 918         case GRAPH_PRE_COMMIT:
 919                 graph_output_pre_commit_line(graph, sb);
 920                 return 0;
 921         case GRAPH_COMMIT:
 922                 graph_output_commit_line(graph, sb);
 923                 return 1;
 924         case GRAPH_POST_MERGE:
 925                 graph_output_post_merge_line(graph, sb);
 926                 return 0;
 927         case GRAPH_COLLAPSING:
 928                 graph_output_collapsing_line(graph, sb);
 929                 return 0;
 930         }
 931
 932         assert(0);
 933         return 0;
 934 }
 935
 936 void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
 937 {
 938         int i, j;
 939
 940         if (graph->state != GRAPH_COMMIT) {
 941                 graph_next_line(graph, sb);
 942                 return;
 943         }
 944
 945         /*
 946          * Output the row containing this commit
 947          * Iterate up to and including graph->num_columns,
 948          * since the current commit may not be in any of the existing
 949          * columns.  (This happens when the current commit doesn't have any
 950          * children that we have already processed.)
 951          */
 952         for (i = 0; i < graph->num_columns; i++) {
 953                 struct commit *col_commit = graph->columns[i].commit;
 954                 if (col_commit == graph->commit) {
 955                         strbuf_addch(sb, '|');
 956
 957                         if (graph->num_parents < 3)
 958                                 strbuf_addch(sb, ' ');
 959                         else {
 960                                 int num_spaces = ((graph->num_parents - 2) * 2);
 961                                 for (j = 0; j < num_spaces; j++)
 962                                         strbuf_addch(sb, ' ');
 963                         }
 964                 } else {
 965                         strbuf_addstr(sb, "| ");
 966                 }
 967         }
 968
 969         graph_pad_horizontally(graph, sb);
 970
 971         /*
 972          * Update graph->prev_state since we have output a padding line
 973          */
 974         graph->prev_state = GRAPH_PADDING;
 975 }
 976
 977 int graph_is_commit_finished(struct git_graph const *graph)
 978 {
 979         return (graph->state == GRAPH_PADDING);
 980 }
 981
 982 void graph_show_commit(struct git_graph *graph)
 983 {
 984         struct strbuf msgbuf;
 985         int shown_commit_line = 0;
 986
 987         if (!graph)
 988                 return;
 989
 990         strbuf_init(&msgbuf, 0);
 991
 992         while (!shown_commit_line) {
 993                 shown_commit_line = graph_next_line(graph, &msgbuf);
 994                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
 995                 if (!shown_commit_line)
 996                         putchar('\n');
 997                 strbuf_setlen(&msgbuf, 0);
 998         }
 999
1000         strbuf_release(&msgbuf);
1001 }
1002
1003 void graph_show_oneline(struct git_graph *graph)
1004 {
1005         struct strbuf msgbuf;
1006
1007         if (!graph)
1008                 return;
1009
1010         strbuf_init(&msgbuf, 0);
1011         graph_next_line(graph, &msgbuf);
1012         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
1013         strbuf_release(&msgbuf);
1014 }
1015
1016 void graph_show_padding(struct git_graph *graph)
1017 {
1018         struct strbuf msgbuf;
1019
1020         if (!graph)
1021                 return;
1022
1023         strbuf_init(&msgbuf, 0);
1024         graph_padding_line(graph, &msgbuf);
1025         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
1026         strbuf_release(&msgbuf);
1027 }
1028
1029 int graph_show_remainder(struct git_graph *graph)
1030 {
1031         struct strbuf msgbuf;
1032         int shown = 0;
1033
1034         if (!graph)
1035                 return 0;
1036
1037         if (graph_is_commit_finished(graph))
1038                 return 0;
1039
1040         strbuf_init(&msgbuf, 0);
1041         for (;;) {
1042                 graph_next_line(graph, &msgbuf);
1043                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
1044                 strbuf_setlen(&msgbuf, 0);
1045                 shown = 1;
1046
1047                 if (!graph_is_commit_finished(graph))
1048                         putchar('\n');
1049                 else
1050                         break;
1051         }
1052         strbuf_release(&msgbuf);
1053
1054         return shown;
1055 }
1056
1057
1058 void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb)
1059 {
1060         char *p;
1061
1062         if (!graph) {
1063                 fwrite(sb->buf, sizeof(char), sb->len, stdout);
1064                 return;
1065         }
1066
1067         /*
1068          * Print the strbuf line by line,
1069          * and display the graph info before each line but the first.
1070          */
1071         p = sb->buf;
1072         while (p) {
1073                 size_t len;
1074                 char *next_p = strchr(p, '\n');
1075                 if (next_p) {
1076                         next_p++;
1077                         len = next_p - p;
1078                 } else {
1079                         len = (sb->buf + sb->len) - p;
1080                 }
1081                 fwrite(p, sizeof(char), len, stdout);
1082                 if (next_p && *next_p != '\0')
1083                         graph_show_oneline(graph);
1084                 p = next_p;
1085         }
1086 }
1087
1088 void graph_show_commit_msg(struct git_graph *graph,
1089                            struct strbuf const *sb)
1090 {
1091         int newline_terminated;
1092
1093         if (!graph) {
1094                 /*
1095                  * If there's no graph, just print the message buffer.
1096                  *
1097                  * The message buffer for CMIT_FMT_ONELINE and
1098                  * CMIT_FMT_USERFORMAT are already missing a terminating
1099                  * newline.  All of the other formats should have it.
1100                  */
1101                 fwrite(sb->buf, sizeof(char), sb->len, stdout);
1102                 return;
1103         }
1104
1105         newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
1106
1107         /*
1108          * Show the commit message
1109          */
1110         graph_show_strbuf(graph, sb);
1111
1112         /*
1113          * If there is more output needed for this commit, show it now
1114          */
1115         if (!graph_is_commit_finished(graph)) {
1116                 /*
1117                  * If sb doesn't have a terminating newline, print one now,
1118                  * so we can start the remainder of the graph output on a
1119                  * new line.
1120                  */
1121                 if (!newline_terminated)
1122                         putchar('\n');
1123
1124                 graph_show_remainder(graph);
1125
1126                 /*
1127                  * If sb ends with a newline, our output should too.
1128                  */
1129                 if (newline_terminated)
1130                         putchar('\n');
1131         }
1132 }