[RFC PATCH] builtin/shortlog: explicitly set hash algo when there is no repo

["Wolfgang Müller" <wolf@oriole.systems>]

Whilst git-shortlog(1) does not explicitly need any repository
information when run without reference to one, it still parses some of
its arguments with parse_revision_opt() which assumes that the hash
algorithm is set. However, in c8aed5e8da (repository: stop setting SHA1
as the default object hash, 2024-05-07) we stopped setting up a default
hash algorithm and instead require commands to set it up explicitly.

This was done for most other commands like in ab274909d4 (builtin/diff:
explicitly set hash algo when there is no repo, 2024-05-07) but was
missed for builtin/shortlog, making git-shortlog(1) segfault outside of
a repository when given arguments like --author that trigger a call to
parse_revision_opt().

Fix this for now by explicitly setting the hash algorithm to SHA1.

Signed-off-by: Wolfgang Müller <wolf@oriole.systems>
---
I think there is a much cleaner patch here if one would look at
disentangling the parsing machinery split between cmd_shortlog() and
parse_revision_opt() such that the latter is only called if there is an
actual repository, but I'm not at all familiar enough with the codebase
to do that. Like the commit says some other commands were fixed like
this as well, so I thought to send this patch your way.

 builtin/shortlog.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index 3ed5c46078..6422f088b2 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -387,6 +387,14 @@ int cmd_shortlog(int argc,
 	struct rev_info rev;
 	int nongit = !startup_info->have_repository;
 
+	/*
+	 * Later on we'll call parse_revision_opt which relies on the hash
+	 * algorithm being set but since we are operating outside of a Git
+	 * repository we cannot determine one. For now default to SHA1.
+	 */
+	if (nongit && !the_hash_algo)
+		repo_set_hash_algo(the_repository, GIT_HASH_SHA1);
+
 	const struct option options[] = {
 		OPT_BIT('c', "committer", &log.groups,
 			N_("group by committer rather than author"),

base-commit: 777489f9e09c8d0dd6b12f9d90de6376330577a2
-- 
2.47.0