Re: [PATCH/RFC] ll-merge: use a longer conflict marker for internal merge

Junio C Hamano [off-list ref] writes:

The primary use of conflict markers is to help the user who resolves
the final (outer) merge by hand to show which part came from which
branch by separating the blocks of lines apart.  When the conflicted
parts from a "virtual ancestor" merge created by merge-recursive
remains in the common ancestor part in the final result, however,
the conflict markers that are the same size as the final merge
become harder to see.

Increase the conflict marker size slightly for these inner merges so
that the markers from the final merge and cruft from internal merge
can be distinguished more easily.

Signed-off-by: Junio C Hamano <redacted>
---
 * This would help reduce the common issue that prevents "rerere"
   from being used on a really complex conflict.  I have another
   (arguably riskier) patch that teaches rerere's parser to ignore
   "<<<" and ">>>" markers that says "Temporary merge branch " at
   the end of the line that achives a similar effect, but I think
   this may be a cleaner solution, partly because it also deals with
   "===" and "|||" lines that do not have such a clue to help
   rerere's parser.

Just for comparison, this is the other "riskier" approach.

-- >8 --
Subject: [PATCH] rerere: try ignoring extra cruft left by merge-recursive

Sometimes the conflict markers from the virtual ancestor synthesis
done by merge-recursive can seep out to the conflicted area of the
final (incomplete) merge result.  Detect and reject them by noticing
the "Temporary merge branch 1" (or "2") branch names.

This is an incomplete solution for "rerere sometimes cannot parse
the conflicted parts" problem, because there is no such helpful clue
on "|||||" (seen only when using "diff3" style) and "=====" lines.

Signed-off-by: Junio C Hamano <redacted>
---
 rerere.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/rerere.c b/rerere.c
index 1693866..02cbc24 100644
--- a/rerere.c
+++ b/rerere.c

@@ -359,6 +359,18 @@ static int rerere_file_getline(struct strbuf *sb, struct rerere_io *io_)
 	return strbuf_getwholeline(sb, io->input, '\n');
 }
 
+static int is_temporary_branch_mark(char *buf)
+{
+	const char *name;
+
+	if (!skip_prefix(buf, " Temporary merge branch ", &name))
+		return 0;
+	if (*name != '1' && *name != '2')
+		return 0;
+	name++;
+	return (!*name || (*name == '\n'));
+}
+
 /*
  * Require the exact number of conflict marker letters, no more, no
  * less, followed by SP or any whitespace

@@ -381,7 +393,7 @@ static int is_cmarker(char *buf, int marker_char, int marker_size)
 	while (marker_size--)
 		if (*buf++ != marker_char)
 			return 0;
-	if (want_sp && *buf != ' ')
+	if (want_sp && (*buf != ' ' || is_temporary_branch_mark(buf)))
 		return 0;
 	return isspace(*buf);
 }

-- 
2.8.1-367-g5b624f2