[PATCH 09/11] builtin/diff: explicitly set hash algo when there is no repo

From

Patrick Steinhardt <ps@pks.im>

Date

Apr 19, 2024, 09:51 UTC

Message-ID

<39e56dab621a2a1e0cbaf67f8de44614c354dcb1.1713519789.git.ps@pks.im>

In-Reply-To

<cover.1713519789.git.ps@pks.im>

```

diff --git a/a b/b
index 7898192..6178079 100644
--- a/a
+++ b/b
@@ -1 +1 @@
-a
+b
```

We implicitly use SHA1 to calculate the hash here, which is because
`the_repository` gets initialized with SHA1 during the startup routine.
We are about to stop doing this though such that `the_repository` only
ever has a hash function when it was properly initialized via a repo's
configuration.

To give full control to our users, we would ideally add a new switch to
git-diff(1) that allows them to specify the hash function when executed
outside of a repository. But for now, we only convert the code to make
this explicit such that we can stop setting the default hash algorithm
for `the_repository`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 builtin/diff.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/builtin/diff.c b/builtin/diff.c
index 6e196e0c7d..58ec7e5da2 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -465,6 +465,15 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 			no_index = DIFF_NO_INDEX_IMPLICIT;
 	}
 
+	/*
+	 * When operating outside of a Git repository we need to have a hash
+	 * algorithm at hand so that we can generate the blob hashes. We
+	 * default to SHA1 here, but may eventually want to change this to be
+	 * configurable via a command line option.
+	 */
+	if (nongit)
+		repo_set_hash_algo(the_repository, GIT_HASH_SHA1);
+
 	init_diff_ui_defaults();
 	git_config(git_diff_ui_config, NULL);
 	prefix = precompose_argv_prefix(argc, argv, prefix);

-- 
2.44.GIT