These patches are an attempt to make Git's startup sequence a bit less
surprising.

The idea here is to discover the .git/ directory gently (i.e. without
changing the current working directory, nor any global variables), and
to use it to read the .git/config file early, before we actually called
setup_git_directory() (if we ever do that).

This also allows us to fix the early config e.g. to determine the pager
or to resolve aliases in a non-surprising manner.

My own use case: in the GVFS Git fork, we need to execute pre-command
and post-command hooks before and after *every* Git command. A previous
version of the pre-command/post-command hook support was broken, as it
used run_hook() which implicitly called setup_git_directory() too early.
The discover_git_directory() function (and due to core.hooksPath also
the read_early_config() function) helped me fix this.

Notable notes:

- Even if it can cause surprising problems, `init` and `clone` are not
  special-cased. Rationale: it would introduce technical debt and
  violate the Principle Of Least Astonishment.

- The read_early_config() function does not cache Git directory
  discovery nor read values. This is left for another patch series, if
  it ever becomes necessary.

- The alias handling in git.c could possibly benefit from this work, but
  again, this is a separate topic from the current patch series.

Changes since v3:

- instead of just fixing the `== '/'` comparison, 2/9 now *also* changes
  the style of the original to something Linux' checkpatch.pl prefers.

- fixed the comment added in 8/9 which was stale from an earlier
  iteration of this patch series.

- adjusted the commit above discover_git_directory()'s declaration, to
  make it more understandable.

- touched up the commit message of 5/9 to make the flow more natural.

- moved a fault fixup: by mistake, the repository_format check was added
  to 8/9 when it really needed to go to 5/9, where the
  discover_git_directory() function was introduced (I noticed this while
  rebasing).

- fixed discover_git_directory() when setup_git_directory_gently_1()
  returned GIT_DIR_NONE (the previous iteration would *not* return NULL
  in that case).

Johannes Schindelin (10):
  t7006: replace dubious test
  setup_git_directory(): use is_dir_sep() helper
  Prepare setup_discovered_git_directory() the root directory
  setup_git_directory_1(): avoid changing global state
  Introduce the discover_git_directory() function
  Make read_early_config() reusable
  read_early_config(): avoid .git/config hack when unneeded
  read_early_config(): really discover .git/
  Test read_early_config()
  setup_git_directory_gently_1(): avoid die()ing

 cache.h                 |   8 ++
 config.c                |  25 +++++
 pager.c                 |  31 ------
 setup.c                 | 246 +++++++++++++++++++++++++++++++++---------------
 t/helper/test-config.c  |  15 +++
 t/t1309-early-config.sh |  50 ++++++++++
 t/t7006-pager.sh        |  18 +++-
 7 files changed, 282 insertions(+), 111 deletions(-)
 create mode 100755 t/t1309-early-config.sh

base-commit: 3bc53220cb2dcf709f7a027a3f526befd021d858

Submitted-As: https://public-inbox.org/git/cover.1488897111.git.johannes.schindelin@gmx.de
In-Reply-To: https://public-inbox.org/git/cover.1488506615.git.johannes.schindelin@gmx.de
In-Reply-To: https://public-inbox.org/git/cover.1481211338.git.johannes.schindelin@gmx.de
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