merge-file: clamp exit code to maximum 127

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 <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-merge-file.txt b/Documentation/git-merge-file.txt
index d2fc12ec77b85a5c9457cbfa160e5c05c1a32f43..f85603261325f6f88b31c30b5fb2bafcded58d92 100644 (file)
--- 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 844f84f40bf0f8b9d95f4e9f0496c010386a9fb8..ab4330a3d0b0099c37acf12dbb3d02bd06b74287 100644 (file)
--- a/builtin/merge-file.c
+++ b/builtin/merge-file.c
@@ -102,5 +102,8 @@ 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 b16462132fd01f21cfd2af40a3c769803b0b7c50..ede496c76b3a1cd4e8d3bb7a0235b2bd1094df7a 100755 (executable)
--- 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