"Pyeron, Jason J CTR (US)" <jason.j.pyeron.ctr@xxxxxxxx> writes:
>> -----Original Message-----
>> From: Junio C Hamano
>> Sent: Tuesday, October 22, 2013 3:51 PM
>>
>
>
> <snip/>
>
>> I would think. You might have a funny chicken-and-egg problem with
>> the signed commit, though. I didn't think that part through.
>
> Respectfully, I do not think there is a chicken and egg situation
> here. Either the user has included a generated id field and value
> in the portion covered by the signature, or the mutation of the
> portion covered by the signature has been modified, hence has an
> invalid signature.
>
> Any user signing their commit, should ensure it is the last
> operation, or be prepared to resign it later.
Thanks, I think I got what you are saying.
I was coming from the existing code, assuming that you have a single
commit without Change Id but has already called do_sign_commit().
That is what the users today will get out of "commit -S". But using
the object name of such a commit as the Change Id, and then creating
a new commit by appending a new Change Id trailer will not work, as
that will break the existing signature.
But you can begin from a single commit without Change Id and without
signature---its object name would be the Change Id. You can add a
new Change Id trailer to record that and sign it while creating a
commit. It conceptually may be a three-step process, but still can be
done inside a single invocation of "git commit --change-id -S".
So a rough outline of the patch to implement it may look like below.
The parsing and passing down of the "--change-id" option is left as
an exercise to interested readers. A real patch may have to add an
extra blank line before the strbuf_addf() if buffer.buf does not end
with a trailer to separate the "Change Id" line from the end of the
existing message body.
commit.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/commit.c b/commit.c
index de16a3c..664ef5d 100644
--- a/commit.c
+++ b/commit.c
@@ -1481,17 +1481,22 @@ static const char commit_utf8_warn[] =
int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
struct commit_list *parents, unsigned char *ret,
const char *author, const char *sign_commit,
- struct commit_extra_header *extra)
+ struct commit_extra_header *extra,
+ unsigned int flags)
{
int result;
int encoding_is_utf8;
struct strbuf buffer;
+ int add_change_id = !!(flags & COMMIT_ADD_CHANGE_ID);
assert_sha1_type(tree, OBJ_TREE);
if (memchr(msg->buf, '\0', msg->len))
return error("a NUL byte in commit log message not allowed.");
+ if (add_change_id && strstr(msg->buf, "\nChange-Id: "))
+ add_change_id = 0; /* already has one */
+
/* Not having i18n.commitencoding is the same as having utf-8 */
encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
@@ -1534,6 +1539,13 @@ int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
if (encoding_is_utf8 && !verify_utf8(&buffer))
fprintf(stderr, commit_utf8_warn);
+ if (add_change_id) {
+ unsigned char change_id[20];
+ if (hash_sha1_file(buffer.buf, buffer.len, commit_type, change_id))
+ return -1;
+ strbuf_addf(&buffer, "Change-Id: %s\n", sha1_to_hex(change_id));
+ }
+
if (sign_commit && do_sign_commit(&buffer, sign_commit))
return -1;
--
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