merge: backport GIT_MERGE_AUTOEDIT support

Even though 1.7.9.x series does not open the editor by default
when merging in general, it does do so in one occassion: when
merging an annotated tag. And worse yet, there is no good way
for older scripts to decline this.

Backport the support for GIT_MERGE_AUTOEDIT environment variable
from 1.7.10 track to help those stuck on 1.7.9.x maintenance
track.

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

diff --git a/Documentation/merge-options.txt b/Documentation/merge-options.txt
index 2bd92c474178559cf03f63ffc19098a76a9cf4e2..5afc99f650b17a6ff660d81ba0687f2f46079f7a 100644 (file)
--- a/Documentation/merge-options.txt
+++ b/Documentation/merge-options.txt
@@ -8,9 +8,19 @@ failed and do not autocommit, to give the user a chance to
 inspect and further tweak the merge result before committing.
 
 --edit::
--e::
+--no-edit::
        Invoke editor before committing successful merge to further
-       edit the default merge message.
+       edit the default merge message. The `--no-edit` option can be
+       used to accept the auto-generated message (this is generally
+       discouraged) when merging an annotated tag, in which case
+       `git merge` automatically spawns the editor so that the result
+       of the GPG verification of the tag can be seen.
++
+Older scripts may depend on the historical behaviour of not allowing the
+user to edit the merge log message. They will see an editor opened when
+they run `git merge` to merge an annotated tag. To make it easier to adjust
+such scripts to the updated behaviour, the environment variable
+`GIT_MERGE_AUTOEDIT` can be set to `no` at the beginning of them.
 
 --ff::
        When the merge resolves as a fast-forward, only update the branch

diff --git a/builtin/merge.c b/builtin/merge.c
index 8018a144688541b6ea178e96fe83206209a2902c..5126443fdfe1dc5113943dd3099ab8d87d84887e 100644 (file)
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1109,6 +1109,33 @@ static void write_merge_state(void)
        close(fd);
 }
 
+static int default_edit_option(void)
+{
+       static const char name[] = "GIT_MERGE_AUTOEDIT";
+       const char *e = getenv(name);
+       struct stat st_stdin, st_stdout;
+
+       if (have_message)
+               /* an explicit -m msg without --[no-]edit */
+               return 0;
+
+       if (e) {
+               int v = git_config_maybe_bool(name, e);
+               if (v < 0)
+                       die("Bad value '%s' in environment '%s'", e, name);
+               return v;
+       }
+
+       /* Use editor if stdin and stdout are the same and is a tty */
+       return (!fstat(0, &st_stdin) &&
+               !fstat(1, &st_stdout) &&
+               isatty(0) && isatty(1) &&
+               st_stdin.st_dev == st_stdout.st_dev &&
+               st_stdin.st_ino == st_stdout.st_ino &&
+               st_stdin.st_mode == st_stdout.st_mode);
+}
+
+
 int cmd_merge(int argc, const char **argv, const char *prefix)
 {
        unsigned char result_tree[20];
@@ -1298,7 +1325,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                    merge_remote_util(commit)->obj &&
                    merge_remote_util(commit)->obj->type == OBJ_TAG) {
                        if (option_edit < 0)
-                               option_edit = 1;
+                               option_edit = default_edit_option();
                        allow_fast_forward = 0;
                }
        }