Re: [PATCH v7 11/31] $GIT_COMMON_DIR: a new environment variable

This variable is intended to support multiple working directories
attached to a repository. Such a repository may have a main working
directory, created by either "git init" or "git clone" and one or more
linked working directories. These working directories and the main
repository share the same repository directory.

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
---

diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 17d2ea6..7629e38 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt

@@ -133,6 +138,11 @@ being a symref to point at the current branch.  Such a state
 is often called 'detached HEAD.'  See linkgit:git-checkout[1]
 for details.

+config::
+       Repository specific configuration file. This file is ignored

+       $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/config" will be
+       used instead.
+
 branches::
        A slightly deprecated way to store shorthands to be used
        to specify a URL to 'git fetch', 'git pull' and 'git push'.

diff --git a/environment.c b/environment.c
index fee12a6..6b74f68 100644
--- a/environment.c
+++ b/environment.c

@@ -149,9 +149,18 @@ static void setup_git_env(void)
                git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
        gitfile = read_gitfile(git_dir);
        git_dir = xstrdup(gitfile ? gitfile : git_dir);
-       git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects", &git_db_env);
-       git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index", &git_index_env);
-       git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts", &git_graft_env);
+       git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+       if (git_common_dir) {
+               git_common_dir_env = 1;
+               git_common_dir = xstrdup(git_common_dir);
+       } else
+               git_common_dir = git_dir;
+       git_object_dir = git_path_from_env(DB_ENVIRONMENT, git_common_dir,
+                                          "objects", &git_db_env);
+       git_index_file = git_path_from_env(INDEX_ENVIRONMENT, git_dir,
+                                          "index", &git_index_env);
+       git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, git_dir,
+                                          "info/grafts", &git_graft_env);

        if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
                check_replace_refs = 0;
        namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));

diff --git a/path.c b/path.c
index 3deb80c..8a6586c 100644
--- a/path.c
+++ b/path.c

@@ -90,6 +90,38 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
                buf->buf[newlen] = '/';
 }

+static const char *common_list[] = {
+       "/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
+       "/objects", "/refs", "/remotes", "/rr-cache", "/svn",
+       "config", "gc.pid", "packed-refs", "shallow",
+       NULL
+};
+
+static void update_common_dir(struct strbuf *buf, int git_dir_len)
+{
+       char *base = buf->buf + git_dir_len;
+       const char **p;
+
+       if (is_dir_file(base, "logs", "HEAD"))
+               return; /* keep this in $GIT_DIR */
+       for (p = common_list; *p; p++) {
+               const char *path = *p;
+               int is_dir = 0;
+               if (*path == '/') {
+                       path++;
+                       is_dir = 1;
+               }
+               if (is_dir && dir_prefix(base, path)) {
+                       replace_dir(buf, git_dir_len, get_git_common_dir());
+                       return;
+               }
+               if (!is_dir && !strcmp(base, path)) {
+                       replace_dir(buf, git_dir_len, get_git_common_dir());
+                       return;
+               }

+       }
+}
+
 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 {
        const char *base = buf->buf + git_dir_len;