Re: FYI: git-am allows creation of empty commits.
- From
Junio C Hamano <junkio@cox.net>
- Date
- Feb 24, 2006, 12:04 UTC
- Message-ID
- <7vy8019d44.fsf@assigned-by-dhcp.cox.net>
- In-Reply-To
- <m18xs1dmp3.fsf@ebiederm.dsl.xmission.com>
ebiederm@xmission.com (Eric W. Biederman) writes:
Show 6 quoted lines
> Is this something that we always want to test for in the porcelain > or do we want to move a check into git-commit-tree? > > For getting a reasonable error message where you have the test > seems to be the only sane place, but having the check deeper > down would be more likely to catch this kind of thing.
I think 99.9% of the time it is a mistake if a single-parented commit has the same tree as its parent commit has, so having a check in commit-tree may not be a bad idea.
If you want to do it, however, you need to be a bit careful about merges. In a multi-parented commit, it is legitimate if the merge result exactly match one of the parents (in fact "git-merge -s ours" can be used to create a merge that matches its first parent).
The commit-tree program is one of the oldest part of the system, and as a mechanism, does not set nor enforce policies like this. It has been more liberal than the best current practice, such as (1) don't do single-parent empty commit; (2) don't list the same parent twice. The second one was introduced in mid-June last year, which is "long after it was invented" in git timescale.
On the other hand, it is more anal than it could be. It does not take a tag that points to a commit to its -p parameter. That's because we did not have tag objects in the beginning, and by the time tags were introduced, nobody ran commit-tree by hand anymore.
-- >8 -- [PATCH] commit-tree: disallow an empty single-parent commit.
Also allow "git-commit-tree -p v2.6.16-rc2", instead of having to say "git-commit-tree -p v2.6.16-rc2^0".
Signed-off-by: Junio C Hamano <junkio@cox.net> ---
diff --git a/commit-tree.c b/commit-tree.c index 88871b0..14a7552 100644 --- a/commit-tree.c +++ b/commit-tree.c @@ -45,12 +45,14 @@ static void check_valid(unsigned char *s { void *buf; char type[20]; + unsigned char real_sha1[20]; unsigned long size; - buf = read_sha1_file(sha1, type, &size); - if (!buf || strcmp(type, expect)) + buf = read_object_with_reference(sha1, expect, &size, real_sha1); + if (!buf) die("%s is not a valid '%s' object", sha1_to_hex(sha1), expect); free(buf); + memcpy(sha1, real_sha1, 20); } /* @@ -75,6 +77,19 @@ static int new_parent(int idx) return 1; } +static int check_empty_commit(const unsigned char *tree_sha1, + const unsigned char *parent_sha1) +{ + unsigned char sha1[20]; + char refit[50]; + sprintf(refit, "%s^{tree}", sha1_to_hex(parent_sha1)); + if (get_sha1(refit, sha1)) + die("cannot determine tree in parent commit."); + if (!memcmp(sha1, tree_sha1, 20)) + return error ("empty commit? aborting."); + return 0; +} + int main(int argc, char **argv) { int i; @@ -105,6 +120,9 @@ int main(int argc, char **argv) } if (!parents) fprintf(stderr, "Committing initial tree %s\n", argv[1]); + if (parents == 1) + if (check_empty_commit(tree_sha1, parent_sha1[0])) + exit(1); init_buffer(&buffer, &size); add_buffer(&buffer, &size, "tree %s\n", sha1_to_hex(tree_sha1));