checkout/fetch/pull/pack-objects: allow `-h` outside a repository

When we taught these commands about the sparse index, we did not account
for the fact that the `cmd_*()` functions _can_ be called without a
gitdir, namely when `-h` is passed to show the usage.

A plausible approach to address this is to move the
`prepare_repo_settings()` calls right after the `parse_options()` calls:
The latter will never return when it handles `-h`, and therefore it is
safe to assume that we have a `gitdir` at that point, as long as the
built-in is marked with the `RUN_SETUP` flag.

However, it is unfortunately not that simple. In `cmd_pack_objects()`,
for example, the repo settings need to be fully populated so that the
command-line options `--sparse`/`--no-sparse` can override them, not the
other way round.

Therefore, we choose to imitate the strategy taken in `cmd_diff()`,
where we simply do not bother to prepare and initialize the repo
settings unless we have a `gitdir`.

This fixes https://github.com/git-for-windows/git/issues/3688

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 17 insertions, 10 deletions

diff --git a/builtin/checkout.c b/builtin/checkout.c
index cc804ba8e1..1c13d7fedb 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1602,9 +1602,10 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 	opts->show_progress = -1;
 
 	git_config(git_checkout_config, opts);
-
-	prepare_repo_settings(the_repository);
-	the_repository->settings.command_requires_full_index = 0;
+	if (the_repository->gitdir) {
+		prepare_repo_settings(the_repository);
+		the_repository->settings.command_requires_full_index = 0;
+	}
 
 	opts->track = BRANCH_TRACK_UNSPECIFIED;
 
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 5f06b21f8e..c8ca4262de 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -2014,8 +2014,10 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 	}
 
 	git_config(git_fetch_config, NULL);
-	prepare_repo_settings(the_repository);
-	the_repository->settings.command_requires_full_index = 0;
+	if (the_repository->gitdir) {
+		prepare_repo_settings(the_repository);
+		the_repository->settings.command_requires_full_index = 0;
+	}
 
 	argc = parse_options(argc, argv, prefix,
 			     builtin_fetch_options, builtin_fetch_usage, 0);
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index ba2006f221..87cb7b45c3 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -3976,9 +3976,11 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 	read_replace_refs = 0;
 
 	sparse = git_env_bool("GIT_TEST_PACK_SPARSE", -1);
-	prepare_repo_settings(the_repository);
-	if (sparse < 0)
-		sparse = the_repository->settings.pack_use_sparse;
+	if (the_repository->gitdir) {
+		prepare_repo_settings(the_repository);
+		if (sparse < 0)
+			sparse = the_repository->settings.pack_use_sparse;
+	}
 
 	reset_pack_idx_option(&pack_idx_opts);
 	git_config(git_pack_config, NULL);
diff --git a/builtin/pull.c b/builtin/pull.c
index 100cbf9fb8..d15007d93f 100644
--- a/builtin/pull.c
+++ b/builtin/pull.c
@@ -994,8 +994,10 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
 		set_reflog_message(argc, argv);
 
 	git_config(git_pull_config, NULL);
-	prepare_repo_settings(the_repository);
-	the_repository->settings.command_requires_full_index = 0;
+	if (the_repository->gitdir) {
+		prepare_repo_settings(the_repository);
+		the_repository->settings.command_requires_full_index = 0;
+	}
 
 	argc = parse_options(argc, argv, prefix, pull_options, pull_usage, 0);