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, or 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.

The first iteration of this patch series still tried to be clever and to
avoid having to disentangle the side effects from the
setup_git_directory_gently_1() function simply by duplicating the logic.

However, Peff suggested in a very short sentence that this would not fly
well.

Little did I know that I would spend the better part of an entire week
on trying to address that innocuous comment! There are simply *so many*
side effects in that code. Who would have thought that a function
called check_repository_format() would set global variables?

But after all that work, I am actually quite a bit satisfied with the
way things turned out.

My dirty little secret is that I actually need this for something else
entirely. I need to patch an internal version of Git to gather
statistics, and to that end I need to read the config before and after
running every Git command. Hence the need for a gentle, and correct
early config.

Notes:

- I do not handle dashed invocations of `init` and `clone` correctly.
  That is, even if `git-init` and `git-clone` clearly do not want to
  read the local config, they do. It does not matter all that much
  because they do not use a pager, but still. It is a wart.

- The read_early_config() function is still called multiple times,
  re-reading all the config files and re-discovering the .git/ directory
  multiple times, which is quite wasteful. I was tempted to take care of
  that but I must not run the danger to spread myself even thinner these
  days. If a patch adding that caching were to fly my way, I'd gladly
  integrate it, of course... ;-)

Changes since v1:

- the discover_git_directory() function is no longer completely separate
  from setup_git_directory(), but a callee of the latter.

- t7006 succeeds now (I removed the incorrect test case in favor of one
  that verifies that setup_git_directory() was not run via the tell-tale
  that the current working directory has not changed when the pager
  runs).

Johannes Schindelin (9):
  t7006: replace dubious test
  setup_git_directory(): use is_dir_sep() helper
  setup_git_directory(): avoid changing global state during discovery
  Export the discover_git_directory() function
  Make read_early_config() reusable
  read_early_config(): special-case builtins that create a repository
  read_early_config(): avoid .git/config hack when unneeded
  read_early_config(): really discover .git/
  Test read_early_config()

 cache.h                 |   4 +-
 config.c                |  36 +++++++++
 git.c                   |   3 +
 pager.c                 |  31 -------
 setup.c                 | 211 +++++++++++++++++++++++++++++++-----------------
 t/helper/test-config.c  |  15 ++++
 t/t1309-early-config.sh |  50 ++++++++++++
 t/t7006-pager.sh        |  18 ++++-
 8 files changed, 257 insertions(+), 111 deletions(-)
 create mode 100755 t/t1309-early-config.sh

base-commit: 3bc53220cb2dcf709f7a027a3f526befd021d858

Submitted-As: 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