xdl_merge(): add optional ancestor label to diff3-style output

The ‘git checkout --conflict=diff3’ command can be used to
present conflicts hunks including text from the common ancestor:

	<<<<<<< ours
	ourside
	|||||||
	original
	=======
	theirside
	>>>>>>> theirs

The added information is helpful for resolving merges by hand, and
merge tools can usually grok it because it is very similar to the
output from diff3 -m.

A subtle change can help more tools to understand the output.  ‘diff3’
includes the name of the merge base on the ||||||| line of the output,
and some tools misparse the conflict hunks without it.  Add a new
xmp->ancestor parameter to xdl_merge() for use with conflict style
XDL_MERGE_DIFF3 as a label on the ||||||| line for any conflict hunks.

If xmp->ancestor is NULL, the output format is unchanged.  Thus, this
change only provides unexposed plumbing for the new feature; it does
not affect the outward behavior of git.

Requested-by: Stefan Monnier <monnier@iro.umontreal.ca>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Acked-by: Bert Wesarg <Bert.Wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index a71763ade835fd93ef291106298647408ada08e9..6eb5fffde128d4503fcb33fc8d1e71ac67fc1a8f 100644 (file)
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -117,6 +117,7 @@ typedef struct s_xmparam {
        int level;
        int favor;
        int style;
+       const char *ancestor;   /* label for orig */
 } xmparam_t;
 
 #define DEFAULT_CONFLICT_MARKER_SIZE 7

diff --git a/xdiff/xmerge.c b/xdiff/xmerge.c
index 87cafa7021468d00a11c72dfdc1df05f1ede0fea..9fc80ad3891f93617ed77308026808c4601a542e 100644 (file)
--- a/xdiff/xmerge.c
+++ b/xdiff/xmerge.c
@@ -145,11 +145,13 @@ static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
 
 static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
                              xdfenv_t *xe2, const char *name2,
+                             const char *name3,
                              int size, int i, int style,
                              xdmerge_t *m, char *dest, int marker_size)
 {
        int marker1_size = (name1 ? strlen(name1) + 1 : 0);
        int marker2_size = (name2 ? strlen(name2) + 1 : 0);
+       int marker3_size = (name3 ? strlen(name3) + 1 : 0);
        int j;
 
        if (marker_size <= 0)
@@ -179,10 +181,15 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
        if (style == XDL_MERGE_DIFF3) {
                /* Shared preimage */
                if (!dest) {
-                       size += marker_size + 1;
+                       size += marker_size + 1 + marker3_size;
                } else {
                        for (j = 0; j < marker_size; j++)
                                dest[size++] = '|';
+                       if (marker3_size) {
+                               dest[size] = ' ';
+                               memcpy(dest + size + 1, name3, marker3_size - 1);
+                               size += marker3_size;
+                       }
                        dest[size++] = '\n';
                }
                size += xdl_orig_copy(xe1, m->i0, m->chg0, 1,
@@ -217,6 +224,7 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 
 static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
                                 xdfenv_t *xe2, const char *name2,
+                                const char *ancestor_name,
                                 int favor,
                                 xdmerge_t *m, char *dest, int style,
                                 int marker_size)
@@ -229,6 +237,7 @@ static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
 
                if (m->mode == 0)
                        size = fill_conflict_hunk(xe1, name1, xe2, name2,
+                                                 ancestor_name,
                                                  size, i, style, m, dest,
                                                  marker_size);
                else if (m->mode & 3) {
@@ -403,6 +412,7 @@ static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1, const char *name1,
                xmparam_t const *xmp, mmbuffer_t *result) {
        xdmerge_t *changes, *c;
        xpparam_t const *xpp = &xmp->xpp;
+       const char *const ancestor_name = xmp->ancestor;
        int i0, i1, i2, chg0, chg1, chg2;
        int level = xmp->level;
        int style = xmp->style;
@@ -540,6 +550,7 @@ static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1, const char *name1,
        if (result) {
                int marker_size = xmp->marker_size;
                int size = xdl_fill_merge_buffer(xe1, name1, xe2, name2,
+                                                ancestor_name,
                                                 favor, changes, NULL, style,
                                                 marker_size);
                result->ptr = xdl_malloc(size);
@@ -548,7 +559,8 @@ static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1, const char *name1,
                        return -1;
                }
                result->size = size;
-               xdl_fill_merge_buffer(xe1, name1, xe2, name2, favor, changes,
+               xdl_fill_merge_buffer(xe1, name1, xe2, name2,
+                                     ancestor_name, favor, changes,
                                      result->ptr, style, marker_size);
        }
        return xdl_cleanup_merge(changes);