[PATCH v2] config.c: split some variables to $GIT_DIR/config.worktree

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

When you define $GIT_DIR/info/config.worktree, which contains of
gitignore-style patterns (*), config variables that match these
patterns will be saved in $GIT_DIR/config.worktree instead of
$GIT_DIR/config.

On the surface, they are just like any other variables. You can read
or modify them with `git config` command, or config_* API. Underneath,
they are always stored in $GIT_DIR/config.worktree instead of
$GIT_DIR/config (and never in $HOME/.gitconfig or /etc/gitconfig)

The reason for this split is, as the name implies, for
worktree-specific configuration. When the same repo is attached to
more than one worktree, we can't use $GIT_DIR/config to store worktree
specific stuff because it's shared across worktrees.

(*) Config variable names are separated by dots. However as this is a
quick and dirty patch to experiment with submodules and multiple
worktrees, you must substitute dots with slashes when writing these
patterns, for now. E.g. write "remote/*/foo" instead of "remote.*.foo"

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Something for Max to play with if he's still experimenting with
 multiple worktree support for submodules :-) It's far from perfect,
 but good enough for this purpose.

 Documentation/config.txt |  6 ++++-
 builtin/config.c         |  8 ++++++
 config.c                 | 67 ++++++++++++++++++++++++++++++++++++++++++++++++
 t/t1300-repo-config.sh   | 34 ++++++++++++++++++++++++
 4 files changed, 114 insertions(+), 1 deletion(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 2700a1b..6d00f49 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -2,11 +2,15 @@ CONFIGURATION FILE
 ------------------
 
 The Git configuration file contains a number of variables that affect
-the Git commands' behavior. The `.git/config` file in each repository
+the Git commands' behavior. The `.git/config` and `.git/config.worktree`
+files in each repository
 is used to store the configuration for that repository, and
 `$HOME/.gitconfig` is used to store a per-user configuration as
 fallback values for the `.git/config` file. The file `/etc/gitconfig`
 can be used to store a system-wide default configuration.
+If `.git/info/core.worktree` exists, it contains gitignore-style
+patterns. Variables that match these patterns can only be contained in
+`.git/config.worktree`.
 
 The configuration variables are used by both the Git plumbing
 and the porcelains. The variables are divided into sections, wherein
diff --git a/builtin/config.c b/builtin/config.c
index 8cc2604..4ca8fc2 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -555,6 +555,14 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 			usage_with_options(builtin_config_usage, builtin_config_options);
 		}
 
+	/*
+	 * For set operations, --local could be either config or
+	 * config.worktree. Let config.c determine the path based on
+	 * config keys.
+	 */
+	if (use_local_config && actions != ACTION_LIST)
+		given_config_source.file = NULL;
+
 	if (actions == ACTION_LIST) {
 		check_argc(argc, 0, 0);
 		if (git_config_with_options(show_all_config, NULL,
diff --git a/config.c b/config.c
index 15a2983..f68eb6a 100644
--- a/config.c
+++ b/config.c
@@ -12,6 +12,7 @@
 #include "quote.h"
 #include "hashmap.h"
 #include "string-list.h"
+#include "dir.h"
 
 struct config_source {
 	struct config_source *prev;
@@ -37,6 +38,7 @@ struct config_source {
 };
 
 static struct config_source *cf;
+static struct exclude_list config_local;
 
 static int zlib_compression_seen;
 
@@ -84,6 +86,34 @@ static long config_buf_ftell(struct config_source *conf)
 	return conf->u.buf.pos;
 }
 
+static int is_config_local(const char *key_)
+{
+	static struct strbuf key = STRBUF_INIT;
+	static int loaded;
+	int i, dtype;
+
+	if (!loaded) {
+		add_excludes_from_file_to_list(git_path("info/config.worktree"),
+					       "", 0, &config_local, 0);
+		loaded = 1;
+	}
+
+	if (!config_local.nr)
+		return 0;
+
+	strbuf_reset(&key);
+	strbuf_addstr(&key, key_);
+	for (i = 0; i < key.len; i++) {
+		if (key.buf[i] == '.')
+			key.buf[i] = '/';
+		else
+			key.buf[i] = tolower(key.buf[i]);
+	}
+	dtype = DT_REG;
+	return is_excluded_from_list(key.buf, key.len, "", &dtype,
+				     &config_local) > 0;
+}
+
 #define MAX_INCLUDE_DEPTH 10
 static const char include_depth_advice[] =
 "exceeded maximum include depth (%d) while including\n"
@@ -1167,6 +1197,15 @@ int git_config_system(void)
 	return !git_env_bool("GIT_CONFIG_NOSYSTEM", 0);
 }
 
+static int config_local_filter(const char *var, const char *value, void *data)
+{
+	struct config_include_data *inc = data;
+
+	if (!is_config_local(var))
+		return error("%s does not belong to config.worktree", var);
+	return inc->fn(var, value, inc->data);
+}
+
 int git_config_early(config_fn_t fn, void *data, const char *repo_config)
 {
 	int ret = 0, found = 0;
@@ -1192,8 +1231,19 @@ int git_config_early(config_fn_t fn, void *data, const char *repo_config)
 	}
 
 	if (repo_config && !access_or_die(repo_config, R_OK, 0)) {
+		char *wt_config;
 		ret += git_config_from_file(fn, repo_config, data);
 		found += 1;
+		wt_config = git_pathdup("config.worktree");
+		if (!access_or_die(wt_config, R_OK, 0)) {
+			struct config_include_data inc = CONFIG_INCLUDE_INIT;
+			inc.fn = fn;
+			inc.data = data;
+			ret += git_config_from_file(config_local_filter,
+						    wt_config, &inc);
+			found += 1;
+		}
+		free(wt_config);
 	}
 
 	switch (git_config_from_parameters(fn, data)) {
@@ -1932,6 +1982,23 @@ int git_config_set_multivar_in_file(const char *config_filename,
 
 	store.multi_replace = multi_replace;
 
+	if (is_config_local(key)) {
+		if (!config_filename)
+			config_filename = filename_buf = git_pathdup("config.worktree");
+		/* cheap trick, but should work 90% of time */
+		else if (!ends_with(config_filename, ".worktree"))
+			die("%s can only be stored in %s",
+			    key, git_path("config.worktree"));
+		else {
+			struct strbuf sb = STRBUF_INIT;
+			strbuf_addstr(&sb, real_path(config_filename));
+			if (strcmp_icase(sb.buf,
+					 real_path(git_path("config.worktree"))))
+				die("%s can only be stored in %s",
+				    key, git_path("config.worktree"));
+			strbuf_release(&sb);
+		}
+	}
 	if (!config_filename)
 		config_filename = filename_buf = git_pathdup("config");
 
diff --git a/t/t1300-repo-config.sh b/t/t1300-repo-config.sh
index 938fc8b..c01effb 100755
--- a/t/t1300-repo-config.sh
+++ b/t/t1300-repo-config.sh
@@ -1179,4 +1179,38 @@ test_expect_success POSIXPERM,PERL 'preserves existing permissions' '
 	  "die q(badrename) if ((stat(q(.git/config)))[2] & 07777) != 0600"
 '
 
+test_expect_success 'setting worktree.foo goes to config.worktree' '
+	test_when_finished "rm .git/config.worktree" &&
+	echo "worktree/*" >.git/info/config.worktree &&
+	git config wOrktree.foo bar &&
+	cat >expect <<\EOF &&
+[wOrktree]
+	foo = bar
+EOF
+	test_cmp expect .git/config.worktree &&
+	test "`git config woRktree.foo`" = bar
+'
+
+test_expect_success 'setting --local worktree.foo goes to config.worktree' '
+	test_when_finished "rm .git/config.worktree" &&
+	echo "worktree/*" >.git/info/config.worktree &&
+	git config --local worKtree.fooo barr &&
+	cat >expect <<\EOF &&
+[worKtree]
+	fooo = barr
+EOF
+	test_cmp expect .git/config.worktree &&
+	test "`git config worktreE.fooo`" = barr
+'
+
+test_expect_success 'setting worktree.foo outside config.worktree' '
+	echo "worktree/*" >.git/info/config.worktree &&
+	test_must_fail git config --global Worktree.foo bar 2>err &&
+	grep config.worktree err &&
+	test_must_fail git config --system workTree.foo bar 2>err &&
+	grep config.worktree err &&
+	test_must_fail git config --file foo.worktree worktree.foo bar 2>err &&
+	grep config.worktree err
+'
+
 test_done
-- 
2.3.0.rc1.137.g477eb31