xdl_merge(): introduce XDL_MERGE_ZEALOUS_ALNUM

When a merge conflicts, there are often common lines that are not really
common, such as empty lines or lines containing a single curly bracket.

With XDL_MERGE_ZEALOUS_ALNUM, we use the following heuristics: when a
hunk does not contain any letters or digits, it is treated as conflicting.

In other words, a conflict which used to look like this:

	<<<<<<<
					a = 1;
	=======
					output();
	>>>>>>>
				}
			}
		}

	<<<<<<<
		output();
	=======
		b = 1;
	>>>>>>>

will look like this with ZEALOUS_ALNUM:

	<<<<<<<
					a = 1;
				}
			}
		}

		output();
	=======
					output();
				}
			}
		}

		b = 1;
	>>>>>>>

To demonstrate this, git-merge-file has been switched from
XDL_MERGE_ZEALOUS to XDL_MERGE_ZEALOUS_ALNUM.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-merge-file.c b/builtin-merge-file.c
index 58deb62ac08507901c40e89aec0cea7fcdc78f1e..adce6d4635a4153428368073677cd74a9bafc045 100644 (file)
--- a/builtin-merge-file.c
+++ b/builtin-merge-file.c
@@ -46,7 +46,7 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
        }
 
        ret = xdl_merge(mmfs + 1, mmfs + 0, names[0], mmfs + 2, names[2],
-                       &xpp, XDL_MERGE_ZEALOUS, &result);
+                       &xpp, XDL_MERGE_ZEALOUS_ALNUM, &result);
 
        for (i = 0; i < 3; i++)
                free(mmfs[i].ptr);

diff --git a/t/t6023-merge-file.sh b/t/t6023-merge-file.sh
index 869e8d559e82b6015999e3967ce6cf77761481b3..79dc58b2ce962ea133c4796d0dff66eb9684b48a 100755 (executable)
--- a/t/t6023-merge-file.sh
+++ b/t/t6023-merge-file.sh
@@ -149,4 +149,14 @@ test_expect_success 'MERGE_ZEALOUS simplifies non-conflicts' '
 
 '
 
+sed -e 's/deerit./&\n\n\n\n/' -e "s/locavit,/locavit;/" < new6.txt > new8.txt
+sed -e 's/deerit./&\n\n\n\n/' -e "s/locavit,/locavit --/" < new7.txt > new9.txt
+
+test_expect_success 'ZEALOUS_ALNUM' '
+
+       ! git merge-file -p new8.txt new5.txt new9.txt > merge.out &&
+       test 1 = $(grep ======= < merge.out | wc -l)
+
+'
+
 test_done

diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index c00ddaa6e987407743d2c8877f9ca6e772f89c86..413082e1fdf537d230a0f58940cee7466b965d0e 100644 (file)
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -53,6 +53,7 @@ extern "C" {
 #define XDL_MERGE_MINIMAL 0
 #define XDL_MERGE_EAGER 1
 #define XDL_MERGE_ZEALOUS 2
+#define XDL_MERGE_ZEALOUS_ALNUM 3
 
 typedef struct s_mmfile {
        char *ptr;

diff --git a/xdiff/xmerge.c b/xdiff/xmerge.c
index ecbdae502c7109f0bc46e00322ae95e8815e90c3..82b3573e7ada8c6df13ac24a78650b80af91ea73 100644 (file)
--- a/xdiff/xmerge.c
+++ b/xdiff/xmerge.c
@@ -248,6 +248,23 @@ static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
        return 0;
 }
 
+static int line_contains_alnum(const char *ptr, long size)
+{
+       while (size--)
+               if (isalnum(*(ptr++)))
+                       return 1;
+       return 0;
+}
+
+static int lines_contain_alnum(xdfenv_t *xe, int i, int chg)
+{
+       for (; chg; chg--, i++)
+               if (line_contains_alnum(xe->xdf2.recs[i]->ptr,
+                               xe->xdf2.recs[i]->size))
+                       return 1;
+       return 0;
+}
+
 /*
  * This function merges m and m->next, marking everything between those hunks
  * as conflicting, too.
@@ -266,7 +283,8 @@ static void xdl_merge_two_conflicts(xdmerge_t *m)
  * it appears simpler -- because it takes up less (or as many) lines --
  * if the lines are moved into the conflicts.
  */
-static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m)
+static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m,
+                                     int simplify_if_no_alnum)
 {
        int result = 0;
 
@@ -282,9 +300,12 @@ static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m)
                begin = m->i1 + m->chg1;
                end = next_m->i1;
 
-               if (m->mode != 0 || next_m->mode != 0 || end - begin > 3)
+               if (m->mode != 0 || next_m->mode != 0 ||
+                   (end - begin > 3 &&
+                    (!simplify_if_no_alnum ||
+                     lines_contain_alnum(xe1, begin, end - begin)))) {
                        m = next_m;
-               else {
+               } else {
                        result++;
                        xdl_merge_two_conflicts(m);
                }
@@ -295,6 +316,8 @@ static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m)
  * level == 0: mark all overlapping changes as conflict
  * level == 1: mark overlapping changes as conflict only if not identical
  * level == 2: analyze non-identical changes for minimal conflict set
+ * level == 3: analyze non-identical changes for minimal conflict set, but
+ *             treat hunks not containing any letter or number as conflicting
  *
  * returns < 0 on error, == 0 for no conflicts, else number of conflicts
  */
@@ -400,7 +423,7 @@ static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1, const char *name1,
        /* refine conflicts */
        if (level > 1 &&
            (xdl_refine_conflicts(xe1, xe2, changes, xpp) < 0 ||
-            xdl_simplify_non_conflicts(xe1, changes) < 0)) {
+            xdl_simplify_non_conflicts(xe1, changes, level > 2) < 0)) {
                xdl_cleanup_merge(changes);
                return -1;
        }