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

As reported in https://github.com/git-for-windows/git/issues/3688, calling git fetch -h outside a repository now results in a very ugly

 BUG: repo-settings.c:23: Cannot add settings for uninitialized repository

The reason is that the prepare_repo_settings() calls (that we introduced to support sparse index) assume that there is a gitdir, but the hack to allow parse_options() to handle -h even outside a repository invalidates that assumption.

One strategy I considered was to move the prepare_repo_settings() calls after parse_options(). This would work because when parse_options() handles -h, it exits without returning.

However, this strategy failed in my tests because e.g. cmd_unpack_objects() does need the pack_use_sparse to be populated correctly before even parsing the options so that it can be overridden via --sparse/--no-sparse.

Hence the current strategy where the code that prepares the repo settings and then accesses them is guarded behind the condition that we must have a gitdir to do so.

Note: There are other instances where prepare_repo_settings() is called before parse_options(), e.g. in cmd_status(), in seen there are even more instances (e.g. cmd_checkout_index()). All of those instances that are not touched by this here patch do have special code to handle -h early, though, before calling prepare_repo_settings() let alone parse_options().

Johannes Schindelin (2):
checkout/fetch/pull/pack-objects: allow -h outside a repository
t0012: verify that built-ins handle -h even without gitdir

 builtin/checkout.c     | 7 ++++---
 builtin/fetch.c        | 6 ++++--
 builtin/pack-objects.c | 8 +++++---
 builtin/pull.c         | 6 ++++--
 t/t0012-help.sh        | 7 ++++++-
 5 files changed, 23 insertions(+), 11 deletions(-)

base-commit: 4c53a8c20f8984adb226293a3ffd7b88c3f4ac1a
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1139%2Fdscho%2Fprepare_repo_settings-after-parse_options-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1139/dscho/prepare_repo_settings-after-parse_options-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1139

Range-diff vs v1:

1: 25d1a2963f2 ! 1: 6e9cdd10a70 checkout/fetch/pull/pack-objects: allow -h outside a repository
@@ builtin/fetch.c: int cmd_fetch(int argc, const char **argv, const char *prefix)

argc = parse_options(argc, argv, prefix,
builtin_fetch_options, builtin_fetch_usage, 0);
-+
- if (recurse_submodules != RECURSE_SUBMODULES_OFF) {
- int *sfjc = submodule_fetch_jobs_config == -1
- ? &submodule_fetch_jobs_config : NULL;

## builtin/pack-objects.c ##
@@ builtin/pack-objects.c: int cmd_pack_objects(int argc, const char **argv, const char *prefix)
2: 49977ff9f4e = 2: 93df4a73dab t0012: verify that built-ins handle -h even without gitdir

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