Merge branch 'nd/per-worktree-config'

A fourth class of configuration files (in addition to the
traditional "system wide", "per user in the $HOME directory" and
"per repository in the $GIT_DIR/config") has been introduced so
that different worktrees that share the same repository (hence the
same $GIT_DIR/config file) can use different customization.

* nd/per-worktree-config:
  worktree: add per-worktree config files
  t1300: extract and use test_cmp_config()

Author: gitster

Documentation/config.txt

@@ -2,8 +2,9 @@ CONFIGURATION FILE
 ------------------
 
 The Git configuration file contains a number of variables that affect
-the Git commands' behavior. The `.git/config` file in each repository
-is used to store the configuration for that repository, and
+the Git commands' behavior. The files `.git/config` and optionally
+`config.worktree` (see `extensions.worktreeConfig` below) in each
+repository are 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.
@@ -291,6 +292,13 @@ include::config/advice.txt[]
 
 include::config/core.txt[]
 
+extensions.worktreeConfig::
+	If set, by default "git config" reads from both "config" and
+	"config.worktree" file from GIT_DIR in that order. In
+	multiple working directory mode, "config" file is shared while
+	"config.worktree" is per-working directory (i.e., it's in
+	GIT_COMMON_DIR/worktrees/<id>/config.worktree)
+
 include::config/add.txt[]
 
 include::config/alias.txt[]

Documentation/git-config.txt

@@ -45,13 +45,15 @@ unset an existing `--type` specifier with `--no-type`.
 
 When reading, the values are read from the system, global and
 repository local configuration files by default, and options
-`--system`, `--global`, `--local` and `--file <filename>` can be
-used to tell the command to read from only that location (see <<FILES>>).
+`--system`, `--global`, `--local`, `--worktree` and
+`--file <filename>` can be used to tell the command to read from only
+that location (see <<FILES>>).
 
 When writing, the new value is written to the repository local
 configuration file by default, and options `--system`, `--global`,
-`--file <filename>` can be used to tell the command to write to
-that location (you can say `--local` but that is the default).
+`--worktree`, `--file <filename>` can be used to tell the command to
+write to that location (you can say `--local` but that is the
+default).
 
 This command will fail with non-zero status upon error.  Some exit
 codes are:
@@ -131,6 +133,11 @@ from all available files.
 +
 See also <<FILES>>.
 
+--worktree::
+	Similar to `--local` except that `.git/config.worktree` is
+	read from or written to if `extensions.worktreeConfig` is
+	present. If not it's the same as `--local`.
+
 -f config-file::
 --file config-file::
 	Use the given config file instead of the one specified by GIT_CONFIG.
@@ -281,6 +288,10 @@ $XDG_CONFIG_HOME/git/config::
 $GIT_DIR/config::
 	Repository specific configuration file.
 
+$GIT_DIR/config.worktree::
+	This is optional and is only searched when
+	`extensions.worktreeConfig` is present in $GIT_DIR/config.
+
 If no further options are given, all reading options will read all of these
 files that are available. If the global or the system-wide configuration
 file are not available they will be ignored. If the repository configuration
@@ -299,9 +310,10 @@ configuration file. Note that this also affects options like `--replace-all`
 and `--unset`. *'git config' will only ever change one file at a time*.
 
 You can override these rules either by command-line options or by environment
-variables. The `--global` and the `--system` options will limit the file used
-to the global or system-wide file respectively. The `GIT_CONFIG` environment
-variable has a similar effect, but you can specify any filename you want.
+variables. The `--global`, `--system` and `--worktree` options will limit
+the file used to the global, system-wide or per-worktree file respectively.
+The `GIT_CONFIG` environment variable has a similar effect, but you
+can specify any filename you want.
 
 
 ENVIRONMENT

Documentation/git-worktree.txt

@@ -204,6 +204,36 @@ working trees, it can be used to identify worktrees. For example if
 you only have two working trees, at "/abc/def/ghi" and "/abc/def/ggg",
 then "ghi" or "def/ghi" is enough to point to the former working tree.
 
+CONFIGURATION FILE
+------------------
+By default, the repository "config" file is shared across all working
+trees. If the config variables `core.bare` or `core.worktree` are
+already present in the config file, they will be applied to the main
+working trees only.
+
+In order to have configuration specific to working trees, you can turn
+on "worktreeConfig" extension, e.g.:
+
+------------
+$ git config extensions.worktreeConfig true
+------------
+
+In this mode, specific configuration stays in the path pointed by `git
+rev-parse --git-path config.worktree`. You can add or update
+configuration in this file with `git config --worktree`. Older Git
+versions will refuse to access repositories with this extension.
+
+Note that in this file, the exception for `core.bare` and `core.worktree`
+is gone. If you have them in $GIT_DIR/config before, you must move
+them to the `config.worktree` of the main working tree. You may also
+take this opportunity to review and move other configuration that you
+do not want to share to all working trees:
+
+ - `core.worktree` and `core.bare` should never be shared
+
+ - `core.sparseCheckout` is recommended per working tree, unless you
+   are sure you always use sparse checkout for all working trees.
+
 DETAILS
 -------
 Each linked working tree has a private sub-directory in the repository's
@@ -253,6 +283,9 @@ to `/path/main/.git/worktrees/test-next` then a file named
 `test-next` entry from being pruned.  See
 linkgit:gitrepository-layout[5] for details.
 
+When extensions.worktreeConfig is enabled, the config file
+`.git/worktrees/<id>/config.worktree` is read after `.git/config` is.
+
 LIST OUTPUT FORMAT
 ------------------
 The worktree list command has two output formats.  The default format shows the

Documentation/gitrepository-layout.txt

@@ -143,6 +143,11 @@ config::
 	if $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/config" will be
 	used instead.
 
+config.worktree::
+	Working directory specific configuration file for the main
+	working directory in multiple working directory setup (see
+	linkgit:git-worktree[1]).
+
 branches::
 	A slightly deprecated way to store shorthands to be used
 	to specify a URL to 'git fetch', 'git pull' and 'git push'.
@@ -275,6 +280,9 @@ worktrees/<id>/locked::
 	or manually by `git worktree prune`. The file may contain a string
 	explaining why the repository is locked.
 
+worktrees/<id>/config.worktree::
+	Working directory specific configuration file.
+
 SEE ALSO
 --------
 linkgit:git-init[1],

builtin/config.c

@@ -5,6 +5,7 @@
 #include "parse-options.h"
 #include "urlmatch.h"
 #include "quote.h"
+#include "worktree.h"
 
 static const char *const builtin_config_usage[] = {
 	N_("git config [<options>]"),
@@ -24,6 +25,7 @@ static char key_delim = ' ';
 static char term = '\n';
 
 static int use_global_config, use_system_config, use_local_config;
+static int use_worktree_config;
 static struct git_config_source given_config_source;
 static int actions, type;
 static char *default_value;
@@ -123,6 +125,7 @@ static struct option builtin_config_options[] = {
 	OPT_BOOL(0, "global", &use_global_config, N_("use global config file")),
 	OPT_BOOL(0, "system", &use_system_config, N_("use system config file")),
 	OPT_BOOL(0, "local", &use_local_config, N_("use repository config file")),
+	OPT_BOOL(0, "worktree", &use_worktree_config, N_("use per-worktree config file")),
 	OPT_STRING('f', "file", &given_config_source.file, N_("file"), N_("use given config file")),
 	OPT_STRING(0, "blob", &given_config_source.blob, N_("blob-id"), N_("read config from given blob object")),
 	OPT_GROUP(N_("Action")),
@@ -602,6 +605,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 			     PARSE_OPT_STOP_AT_NON_OPTION);
 
 	if (use_global_config + use_system_config + use_local_config +
+	    use_worktree_config +
 	    !!given_config_source.file + !!given_config_source.blob > 1) {
 		error(_("only one config file at a time"));
 		usage_builtin_config();
@@ -645,7 +649,20 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		given_config_source.file = git_etc_gitconfig();
 	else if (use_local_config)
 		given_config_source.file = git_pathdup("config");
-	else if (given_config_source.file) {
+	else if (use_worktree_config) {
+		struct worktree **worktrees = get_worktrees(0);
+		if (repository_format_worktree_config)
+			given_config_source.file = git_pathdup("config.worktree");
+		else if (worktrees[0] && worktrees[1])
+			die(_("--worktree cannot be used with multiple "
+			      "working trees unless the config\n"
+			      "extension worktreeConfig is enabled. "
+			      "Please read \"CONFIGURATION FILE\"\n"
+			      "section in \"git help worktree\" for details"));
+		else
+			given_config_source.file = git_pathdup("config");
+		free_worktrees(worktrees);
+	} else if (given_config_source.file) {
 		if (!is_absolute_path(given_config_source.file) && prefix)
 			given_config_source.file =
 				prefix_filename(prefix, given_config_source.file);

cache.h

@@ -962,11 +962,13 @@ extern int grafts_replace_parents;
 extern int repository_format_precious_objects;
 extern char *repository_format_partial_clone;
 extern const char *core_partial_clone_filter_default;
+extern int repository_format_worktree_config;
 
 struct repository_format {
 	int version;
 	int precious_objects;
 	char *partial_clone; /* value of extensions.partialclone */
+	int worktree_config;
 	int is_bare;
 	int hash_algo;
 	char *work_tree;

config.c

@@ -1695,6 +1695,17 @@ static int do_git_config_sequence(const struct config_options *opts,
 	if (repo_config && !access_or_die(repo_config, R_OK, 0))
 		ret += git_config_from_file(fn, repo_config, data);
 
+	/*
+	 * Note: this should have a new scope, CONFIG_SCOPE_WORKTREE.
+	 * But let's not complicate things before it's actually needed.
+	 */
+	if (repository_format_worktree_config) {
+		char *path = git_pathdup("config.worktree");
+		if (!access_or_die(path, R_OK, 0))
+			ret += git_config_from_file(fn, path, data);
+		free(path);
+	}
+
 	current_parsing_scope = CONFIG_SCOPE_CMDLINE;
 	if (git_config_from_parameters(fn, data) < 0)
 		die(_("unable to parse command-line config"));

environment.c

@@ -33,6 +33,7 @@ int ref_paranoia = -1;
 int repository_format_precious_objects;
 char *repository_format_partial_clone;
 const char *core_partial_clone_filter_default;
+int repository_format_worktree_config;
 const char *git_commit_encoding;
 const char *git_log_output_encoding;
 const char *apply_default_whitespace;

setup.c

@@ -402,6 +402,20 @@ void setup_work_tree(void)
 	initialized = 1;
 }
 
+static int read_worktree_config(const char *var, const char *value, void *vdata)
+{
+	struct repository_format *data = vdata;
+
+	if (strcmp(var, "core.bare") == 0) {
+		data->is_bare = git_config_bool(var, value);
+	} else if (strcmp(var, "core.worktree") == 0) {
+		if (!value)
+			return config_error_nonbool(var);
+		data->work_tree = xstrdup(value);
+	}
+	return 0;
+}
+
 static int check_repo_format(const char *var, const char *value, void *vdata)
 {
 	struct repository_format *data = vdata;
@@ -423,16 +437,13 @@ static int check_repo_format(const char *var, const char *value, void *vdata)
 			if (!value)
 				return config_error_nonbool(var);
 			data->partial_clone = xstrdup(value);
-		} else
+		} else if (!strcmp(ext, "worktreeconfig"))
+			data->worktree_config = git_config_bool(var, value);
+		else
 			string_list_append(&data->unknown_extensions, ext);
-	} else if (strcmp(var, "core.bare") == 0) {
-		data->is_bare = git_config_bool(var, value);
-	} else if (strcmp(var, "core.worktree") == 0) {
-		if (!value)
-			return config_error_nonbool(var);
-		data->work_tree = xstrdup(value);
 	}
-	return 0;
+
+	return read_worktree_config(var, value, vdata);
 }
 
 static int check_repository_format_gently(const char *gitdir, struct repository_format *candidate, int *nongit_ok)
@@ -466,7 +477,20 @@ static int check_repository_format_gently(const char *gitdir, struct repository_
 
 	repository_format_precious_objects = candidate->precious_objects;
 	repository_format_partial_clone = candidate->partial_clone;
+	repository_format_worktree_config = candidate->worktree_config;
 	string_list_clear(&candidate->unknown_extensions, 0);
+
+	if (repository_format_worktree_config) {
+		/*
+		 * pick up core.bare and core.worktree from per-worktree
+		 * config if present
+		 */
+		strbuf_addf(&sb, "%s/config.worktree", gitdir);
+		git_config_from_file(read_worktree_config, sb.buf, candidate);
+		strbuf_release(&sb);
+		has_common = 0;
+	}
+
 	if (!has_common) {
 		if (candidate->is_bare != -1) {
 			is_bare_repository_cfg = candidate->is_bare;