Git-merge-file is documented to return one of three exit
codes:
- zero means the merge was successful
- a negative number means an error occurred
- a positive number indicates the number of conflicts
Unfortunately, this all gets stuffed into an 8-bit return
code. Which means that if you have 256 conflicts, this wraps
to zero, and the merge appears to succeed (and commits a
blob full of conflict-marker cruft!).
This patch clamps the return value to a maximum of 127,
which we should be able to safely represent everywhere. This
also leaves 128-255 for other values. Shells (and some parts
of git) will typically represent signal death as 128 plus
the signal number. And negative values are typically coerced
to an 8-bit unsigned value (so "return -1" ends up as 255).
Technically negative returns have the same problem (e.g.,
"-256" wraps back to 0), but this is not a problem in
practice, as the only negative value we use is "-1".
Signed-off-by: Jeff King <p...@peff.net>
---
This can be triggered when using the "resolve" strategy, though I found
it when comparing the results of git-merge-index with libgit2's merge
driver across a large number of GitHub merges (git claimed to
successfully merge but libgit2 correctly identified the conflict). The
real world case that triggered it had exactly 768 conflicts.
Documentation/git-merge-file.txt | 3 ++-
builtin/merge-file.c | 3 +++
t/t7600-merge.sh | 33 +++++++++++++++++++++++++++++++++
3 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/Documentation/git-merge-file.txt b/Documentation/git-merge-file.txt
index d2fc12e..f856032 100644
--- a/Documentation/git-merge-file.txt
+++ b/Documentation/git-merge-file.txt
@@ -41,7 +41,8 @@ lines from `<other-file>`, or lines from both respectively.
The length of the
conflict markers can be given with the `--marker-size` option.
The exit value of this program is negative on error, and the number of
-conflicts otherwise. If the merge was clean, the exit value is 0.
+conflicts otherwise (truncated to 127 if there are more than that many
+conflicts). If the merge was clean, the exit value is 0.
'git merge-file' is designed to be a minimal clone of RCS 'merge'; that is, it
implements all of RCS 'merge''s functionality which is needed by
diff --git a/builtin/merge-file.c b/builtin/merge-file.c
index 50d0bc8..5544705 100644
--- a/builtin/merge-file.c
+++ b/builtin/merge-file.c
@@ -104,5 +104,8 @@ int cmd_merge_file(int argc, const char **argv, const char
*prefix)
free(result.ptr);
}
+ if (ret > 127)
+ ret = 127;
+
return ret;
}
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index 75c50ee..302e238 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -692,4 +692,37 @@ test_expect_success GPG 'merge --no-edit tag should skip
editor' '
test_cmp actual expect
'
+test_expect_success 'set up mod-256 conflict scenario' '
+ # 256 near-identical stanzas...
+ for i in $(test_seq 1 256); do
+ for j in 1 2 3 4 5; do
+ echo $i-$j
+ done
+ done >file &&
+ git add file &&
+ git commit -m base &&
+
+ # one side changes the first line of each to "master"
+ sed s/-1/-master/ <file >tmp &&
+ mv tmp file &&
+ git commit -am master &&
+
+ # and the other to "side"; merging the two will
+ # yield 256 separate conflicts
+ git checkout -b side HEAD^ &&
+ sed s/-1/-side/ <file >tmp &&
+ mv tmp file &&
+ git commit -am side
+'
+
+test_expect_success 'merge detects mod-256 conflicts (recursive)' '
+ git reset --hard &&
+ test_must_fail git merge -s recursive master
+'
+
+test_expect_success 'merge detects mod-256 conflicts (resolve)' '
+ git reset --hard &&
+ test_must_fail git merge -s resolve master
+'
+
test_done
--
2.6.2.572.g6ed22dd
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