[PATCH v2 6/6] config: respect commondir

[Brandon Williams <bmwill@google.com>]

Worktrees present an interesting problem when it comes to the config.
Historically we could assume that the per-repository config lives at
'gitdir/config', but since worktrees were introduced this isn't the case
anymore.  There is currently no way to specify per-worktree
configuration, and as such the repository config is shared with all
worktrees and is located at 'commondir/config'.

Many users of the config machinery correctly set
'config_options.git_dir' with the repository's commondir, allowing the
config to be properly loaded when operating in a worktree.  But other's,
like 'read_early_config()', set 'config_options.git_dir' with the
repository's gitdir which can be incorrect when using worktrees.

To fix this issue, and to make things less ambiguous, lets add a
'commondir' field to the 'config_options' struct and have all callers
properly set both the 'git_dir' and 'commondir' fields so that the
config machinery is able to properly find the repository's config.

Signed-off-by: Brandon Williams <bmwill@google.com>
---
 builtin/config.c |  6 ++++--
 config.c         | 18 ++++++++++++------
 config.h         |  1 +
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/builtin/config.c b/builtin/config.c
index f06a8dff2..8b6e227c5 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -539,8 +539,10 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		config_options.respect_includes = !given_config_source.file;
 	else
 		config_options.respect_includes = respect_includes_opt;
-	if (!nongit)
-		config_options.git_dir = get_git_common_dir();
+	if (!nongit) {
+		config_options.commondir = get_git_common_dir();
+		config_options.git_dir = get_git_dir();
+	}
 
 	if (end_null) {
 		term = '\0';
diff --git a/config.c b/config.c
index 9aa9b9715..81151fb54 100644
--- a/config.c
+++ b/config.c
@@ -1544,8 +1544,8 @@ static int do_git_config_sequence(const struct config_options *opts,
 	char *user_config = expand_user_path("~/.gitconfig", 0);
 	char *repo_config;
 
-	if (opts->git_dir)
-		repo_config = mkpathdup("%s/config", opts->git_dir);
+	if (opts->commondir)
+		repo_config = mkpathdup("%s/config", opts->commondir);
 	else
 		repo_config = NULL;
 
@@ -1609,8 +1609,11 @@ static void git_config_raw(config_fn_t fn, void *data)
 	struct config_options opts = {0};
 
 	opts.respect_includes = 1;
-	if (have_git_dir())
-		opts.git_dir = get_git_common_dir();
+	if (have_git_dir()) {
+		opts.commondir = get_git_common_dir();
+		opts.git_dir = get_git_dir();
+	}
+
 	if (git_config_with_options(fn, data, NULL, &opts) < 0)
 		/*
 		 * git_config_with_options() normally returns only
@@ -1657,7 +1660,8 @@ void read_early_config(config_fn_t cb, void *data)
 
 	opts.respect_includes = 1;
 
-	if (have_git_dir())
+	if (have_git_dir()) {
+		opts.commondir = get_git_common_dir();
 		opts.git_dir = get_git_dir();
 	/*
 	 * When setup_git_directory() was not yet asked to discover the
@@ -1667,8 +1671,10 @@ void read_early_config(config_fn_t cb, void *data)
 	 * notably, the current working directory is still the same after the
 	 * call).
 	 */
-	else if (discover_git_directory(&commondir, &gitdir))
+	} else if (discover_git_directory(&commondir, &gitdir)) {
+		opts.commondir = commondir.buf;
 		opts.git_dir = gitdir.buf;
+	}
 
 	git_config_with_options(cb, data, NULL, &opts);
 
diff --git a/config.h b/config.h
index c70599bd5..63b92784c 100644
--- a/config.h
+++ b/config.h
@@ -30,6 +30,7 @@ enum config_origin_type {
 
 struct config_options {
 	unsigned int respect_includes : 1;
+	const char *commondir;
 	const char *git_dir;
 };
 
-- 
2.13.1.518.g3df882009-goog