[PATCH v5 0/3] config: allow overriding global/system config

Hi,

this is the fifth version of my patch series to provide a way of overriding the global system configuration.

Changes to v4:

    - Readded the call to `git_config_system()`, which I've previously
      dropped by accident. I didn't move it into the new
      `git_system_config()` function as it would change semantics of
      `git config --system`.

    - Added a testcase which verifies that GIT_CONFIG_NOSYSTEM and
      GIT_CONFIG_SYSTEM properly interact with each other: if
      GIT_CONFIG_NOSYSTEM is set, no system-level configuration shall be
      read. This is different than the tests for `git config --system`
      which used to and still does ignore GIT_CONFIG_NOSYSTEM.

    - Small fixups for another testcase to drop needless redirects and
      the `sane_unset` of GIT_CONFIG_NOSYSTEM.

Patrick

Patrick Steinhardt (3):
  config: rename `git_etc_config()`
  config: unify code paths to get global config paths
  config: allow overriding of global and system configuration

 Documentation/git-config.txt |  5 +++
 Documentation/git.txt        | 10 +++++
 builtin/config.c             |  6 +--
 config.c                     | 41 ++++++++++++-----
 config.h                     |  4 +-
 t/t1300-config.sh            | 86 ++++++++++++++++++++++++++++++++++++
 6 files changed, 136 insertions(+), 16 deletions(-)

Range-diff against v4:
1:  34bdbc27d6 ! 1:  1e8899408a config: rename `git_etc_config()`
    @@ config.c: static int do_git_config_sequence(const struct config_options *opts,
     -						  ACCESS_EACCES_OK : 0))
     -		ret += git_config_from_file(fn, git_etc_gitconfig(),
     -					    data);
    -+	if (system_config && !access_or_die(system_config, R_OK,
    -+					    opts->system_gently ?
    -+					    ACCESS_EACCES_OK : 0))
    ++	if (git_config_system() && system_config &&
    ++	    !access_or_die(system_config, R_OK,
    ++			   opts->system_gently ? ACCESS_EACCES_OK : 0))
     +		ret += git_config_from_file(fn, system_config, data);
      
      	current_parsing_scope = CONFIG_SCOPE_GLOBAL;
2:  30f18679bd = 2:  39468f45d2 config: unify code paths to get global config paths
3:  d27efc0aa8 ! 3:  7e7506217e config: allow overriding of global and system configuration
    @@ t/t1300-config.sh: test_expect_success '--show-scope with --show-origin' '
     +'
     +
     +test_expect_success 'override global and system config with missing file' '
    -+	sane_unset GIT_CONFIG_NOSYSTEM &&
    -+	test_must_fail env GIT_CONFIG_GLOBAL=does-not-exist GIT_CONFIG_SYSTEM=/dev/null git config --global --list >actual &&
    -+	test_must_fail env GIT_CONFIG_GLOBAL=/dev/null GIT_CONFIG_SYSTEM=does-not-exist git config --system --list >actual &&
    ++	test_must_fail env GIT_CONFIG_GLOBAL=does-not-exist GIT_CONFIG_SYSTEM=/dev/null git config --global --list &&
    ++	test_must_fail env GIT_CONFIG_GLOBAL=/dev/null GIT_CONFIG_SYSTEM=does-not-exist git config --system --list &&
     +	GIT_CONFIG_GLOBAL=does-not-exist GIT_CONFIG_SYSTEM=does-not-exist git version
     +'
     +
    ++test_expect_success 'system override has no effect with GIT_CONFIG_NOSYSTEM' '
    ++	# `git config --system` has different semantics compared to other
    ++	# commands as it ignores GIT_CONFIG_NOSYSTEM. We thus test whether the
    ++	# variable has an effect via a different proxy.
    ++	cat >alias-config <<-EOF &&
    ++	[alias]
    ++		hello-world = !echo "hello world"
    ++	EOF
    ++	test_must_fail env GIT_CONFIG_NOSYSTEM=true GIT_CONFIG_SYSTEM=alias-config \
    ++		git hello-world &&
    ++	GIT_CONFIG_NOSYSTEM=false GIT_CONFIG_SYSTEM=alias-config \
    ++		git hello-world >actual &&
    ++	echo "hello world" >expect &&
    ++	test_cmp expect actual
    ++'
    ++
     +test_expect_success 'write to overridden global and system config' '
     +	cat >expect <<EOF &&
     +[config]