Op do 15 feb 2024 om 16:04 schreef Jeff King <peff@xxxxxxxx>:
>
> On Thu, Feb 15, 2024 at 08:46:02AM +0100, Maarten Bosmans wrote:
>
> > > How about:
> > >
> > > cat some_commit_ids |
> > > git show --stdin -s -z --format='%H%n%N'
> > >
> > Wouldn't that fail horribly with non-text blobs?
>
> Yes, if you have NULs embedded in your notes then it won't work. Any
> batch output format would require byte counts, then. If we wanted to add
> a feature to support that, I would suggest one of:
>
> - teach the pretty-print formatter a new placeholder to output the
> number of bytes in an element. Then you could do something like
> "%H %(size:%N)%n%N", but it would be generally useful for other
> cases, too.
>
> - teach the pretty-print formatter a variant of %N that outputs only
> the oid of the note, note the note content itself. And then you
> could do something like:
>
> git log --format='%(note:oid) %H' |
> git cat-file --batch='%(objectname) %(objectsize) %(rest)'
>
> to get the usual cat-file output of each note blob, but associated
> with the commit it's attached to (the "%(rest)" placeholder for
> cat-file just relays any text found after the object name of each
> line). You might need to do some scripting between the two to handle
> commits with no note.
>
> Of the two, I'd guess that the second one is a lot less work to
> implement (on the Git side; on the reading side it's a little more
> involved, but still should be a constant number of processes).
The second one is attractive for another reason than implementation
simplicity. While the first one offers more flexibility, the second
reuses the existing cat-file batch format, so the interface between
git and scripts is familiar and consistent.
> One variant of the second one is to use "git notes list". For example,
> you can get all notes via cat-file like this right now:
>
> git notes list |
> git cat-file --batch='%(objectname) %(objectsize) %(rest)'
So the cat-file batch output is suitable for blobs containing newline
or NUL characters. But I struggle a bit with what would be an easy way
of using this format in a shell script. Something with multiple read
and read -N commands reading from the output, I guess.
The git codebase has `extract_batch_output()` in t1006. This uses a
separate perl invocation to parse the cat-file output, which confirms
my suspicion there isn't a straight-forward way to do this in e.g.
just a bash script.
That was why my first steps were to accept that a launching a separate
process per note in a bash loop is a pretty clear and well understood
idiom in shell scripts and try to make the git part of that a bit more
efficient.
> You can get individual notes by asking for "git notes list <commit>",
> but it will only take one at a time. So another easy patch would be
> something like (indentation left funny to make the diff more readable):
>
> diff --git a/builtin/notes.c b/builtin/notes.c
> index e65cae0bcf..5fdad5fb8f 100644
> --- a/builtin/notes.c
> +++ b/builtin/notes.c
> @@ -446,22 +446,22 @@ static int list(int argc, const char **argv, const char *prefix)
> argc = parse_options(argc, argv, prefix, options,
> git_notes_list_usage, 0);
>
> - if (1 < argc) {
> - error(_("too many arguments"));
> - usage_with_options(git_notes_list_usage, options);
> - }
> -
> t = init_notes_check("list", 0);
> if (argc) {
> - if (repo_get_oid(the_repository, argv[0], &object))
> - die(_("failed to resolve '%s' as a valid ref."), argv[0]);
> + retval = 0;
> + while (*++argv) {
> + if (repo_get_oid(the_repository, *argv, &object))
> + die(_("failed to resolve '%s' as a valid ref."), *argv);
> note = get_note(t, &object);
> if (note) {
> - puts(oid_to_hex(note));
> - retval = 0;
> + if (argc > 1)
> + printf("%s %s\n", oid_to_hex(note), oid_to_hex(&object));
> + else
> + puts(oid_to_hex(note));
> } else
> - retval = error(_("no note found for object %s."),
> + retval |= error(_("no note found for object %s."),
> oid_to_hex(&object));
> + }
> } else
> retval = for_each_note(t, 0, list_each_note, NULL);
>
>
> That would allow:
>
> git rev-list ... |
> xargs git notes list |
> git cat-file --batch='%(objectname) %(objectsize) %(rest)'
>
> We could even add a "--stdin" mode to avoid the use of xargs.
Yes, a --stdin mode for `git notes list` would be a useful building
block for scripting indeed.
I'll probably give it a try when this patch series succeeds.
Maarten
