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builtin-commit: use reduce_heads() only when appropriate

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Since commit 6bb6b034 (builtin-commit: use commit_tree(), 2008-09-10),
builtin-commit performs a reduce_heads() unconditionally.  However,
it's not always needed, and in some cases even harmful.

reduce_heads() is not needed for the initial commit or for an
"ordinary" commit, because they don't have any or have only one
parent, respectively.

reduce_heads() must be avoided when 'git commit' is run after a 'git
merge --no-ff --no-commit', otherwise it will turn the
non-fast-forward merge into fast-forward.  For the same reason,
reduce_heads() must be avoided when amending such a merge commit.

To resolve this issue, 'git merge' will write info about whether
fast-forward is allowed or not to $GIT_DIR/MERGE_MODE.  Based on this
info, 'git commit' will only perform reduce_heads() when it's
committing a merge and fast-forward is enabled.

Also add test cases to ensure that non-fast-forward merges are
committed and amended properly.

Signed-off-by: Miklos Vajna <vmiklos@frugalware.org>
Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
This commit is contained in:
Miklos Vajna
2008-10-03 14:04:47 +02:00
committed by Shawn O. Pearce
parent 52e8370bc7
commit cf10f9fdd5
4 changed files with 41 additions and 2 deletions
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16
builtin-commit.c
View File

@ -937,6 +937,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
unsigned char commit_sha1[20];
struct ref_lock *ref_lock;
struct commit_list *parents = NULL, **pptr = &parents;
struct stat statbuf;
int allow_fast_forward = 1;
git_config(git_commit_config, NULL);
@ -951,6 +953,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
return 1;
}
strbuf_init(&sb, 0);
/* Determine parents */
if (initial_commit) {
reflog_msg = "commit (initial)";
@ -984,14 +987,22 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
}
fclose(fp);
strbuf_release(&m);
if (!stat(git_path("MERGE_MODE"), &statbuf)) {
if (strbuf_read_file(&sb, git_path("MERGE_MODE"), 0) < 0)
die("could not read MERGE_MODE: %s",
strerror(errno));
if (!strcmp(sb.buf, "no-ff"))
allow_fast_forward = 0;
}
if (allow_fast_forward)
parents = reduce_heads(parents);
} else {
reflog_msg = "commit";
pptr = &commit_list_insert(lookup_commit(head_sha1), pptr)->next;
}
parents = reduce_heads(parents);
/* Finally, get the commit message */
strbuf_init(&sb, 0);
strbuf_reset(&sb);
if (strbuf_read_file(&sb, git_path(commit_editmsg), 0) < 0) {
rollback_index_files();
die("could not read commit message");
@ -1040,6 +1051,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
unlink(git_path("MERGE_HEAD"));
unlink(git_path("MERGE_MSG"));
unlink(git_path("MERGE_MODE"));
unlink(git_path("SQUASH_MSG"));
if (commit_index_files())