--- /dev/null
+#include "cache.h"
+#include "repository.h"
+
+/* The main repository */
+static struct repository the_repo;
+struct repository *the_repository = &the_repo;
+
+static char *git_path_from_env(const char *envvar, const char *git_dir,
+ const char *path, int fromenv)
+{
+ if (fromenv) {
+ const char *value = getenv(envvar);
+ if (value)
+ return xstrdup(value);
+ }
+
+ return xstrfmt("%s/%s", git_dir, path);
+}
+
+static int find_common_dir(struct strbuf *sb, const char *gitdir, int fromenv)
+{
+ if (fromenv) {
+ const char *value = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+ if (value) {
+ strbuf_addstr(sb, value);
+ return 1;
+ }
+ }
+
+ return get_common_dir_noenv(sb, gitdir);
+}
+
+static void repo_setup_env(struct repository *repo)
+{
+ struct strbuf sb = STRBUF_INIT;
+
+ repo->different_commondir = find_common_dir(&sb, repo->gitdir,
+ !repo->ignore_env);
+ repo->commondir = strbuf_detach(&sb, NULL);
+ repo->objectdir = git_path_from_env(DB_ENVIRONMENT, repo->commondir,
+ "objects", !repo->ignore_env);
+ repo->graft_file = git_path_from_env(GRAFT_ENVIRONMENT, repo->commondir,
+ "info/grafts", !repo->ignore_env);
+ repo->index_file = git_path_from_env(INDEX_ENVIRONMENT, repo->gitdir,
+ "index", !repo->ignore_env);
+}
+
+void repo_set_gitdir(struct repository *repo, const char *path)
+{
+ const char *gitfile = read_gitfile(path);
+
+ /*
+ * NEEDSWORK: Eventually we want to be able to free gitdir and the rest
+ * of the environment before reinitializing it again, but we have some
+ * crazy code paths where we try to set gitdir with the current gitdir
+ * and we don't want to free gitdir before copying the passed in value.
+ */
+ repo->gitdir = xstrdup(gitfile ? gitfile : path);
+
+ repo_setup_env(repo);
+}
+
+/*
+ * Attempt to resolve and set the provided 'gitdir' for repository 'repo'.
+ * Return 0 upon success and a non-zero value upon failure.
+ */
+static int repo_init_gitdir(struct repository *repo, const char *gitdir)
+{
+ int ret = 0;
+ int error = 0;
+ char *abspath = NULL;
+ const char *resolved_gitdir;
+
+ abspath = real_pathdup(gitdir, 0);
+ if (!abspath) {
+ ret = -1;
+ goto out;
+ }
+
+ /* 'gitdir' must reference the gitdir directly */
+ resolved_gitdir = resolve_gitdir_gently(abspath, &error);
+ if (!resolved_gitdir) {
+ ret = -1;
+ goto out;
+ }
+
+ repo_set_gitdir(repo, resolved_gitdir);
+
+out:
+ free(abspath);
+ return ret;
+}
+
+void repo_set_worktree(struct repository *repo, const char *path)
+{
+ repo->worktree = real_pathdup(path, 1);
+}
+
+static int read_and_verify_repository_format(struct repository_format *format,
+ const char *commondir)
+{
+ int ret = 0;
+ struct strbuf sb = STRBUF_INIT;
+
+ strbuf_addf(&sb, "%s/config", commondir);
+ read_repository_format(format, sb.buf);
+ strbuf_reset(&sb);
+
+ if (verify_repository_format(format, &sb) < 0) {
+ warning("%s", sb.buf);
+ ret = -1;
+ }
+
+ strbuf_release(&sb);
+ return ret;
+}
+
+/*
+ * Initialize 'repo' based on the provided 'gitdir'.
+ * Return 0 upon success and a non-zero value upon failure.
+ */
+int repo_init(struct repository *repo, const char *gitdir, const char *worktree)
+{
+ struct repository_format format;
+ memset(repo, 0, sizeof(*repo));
+
+ repo->ignore_env = 1;
+
+ if (repo_init_gitdir(repo, gitdir))
+ goto error;
+
+ if (read_and_verify_repository_format(&format, repo->commondir))
+ goto error;
+
+ if (worktree)
+ repo_set_worktree(repo, worktree);
+
+ return 0;
+
+error:
+ repo_clear(repo);
+ return -1;
+}
+
+void repo_clear(struct repository *repo)
+{
+ free(repo->gitdir);
+ repo->gitdir = NULL;
+ free(repo->commondir);
+ repo->commondir = NULL;
+ free(repo->objectdir);
+ repo->objectdir = NULL;
+ free(repo->graft_file);
+ repo->graft_file = NULL;
+ free(repo->index_file);
+ repo->index_file = NULL;
+ free(repo->worktree);
+ repo->worktree = NULL;
+}
--- /dev/null
+#ifndef REPOSITORY_H
+#define REPOSITORY_H
+
+struct repository {
+ /* Environment */
+ /*
+ * Path to the git directory.
+ * Cannot be NULL after initialization.
+ */
+ char *gitdir;
+
+ /*
+ * Path to the common git directory.
+ * Cannot be NULL after initialization.
+ */
+ char *commondir;
+
+ /*
+ * Path to the repository's object store.
+ * Cannot be NULL after initialization.
+ */
+ char *objectdir;
+
+ /*
+ * Path to the repository's graft file.
+ * Cannot be NULL after initialization.
+ */
+ char *graft_file;
+
+ /*
+ * Path to the current worktree's index file.
+ * Cannot be NULL after initialization.
+ */
+ char *index_file;
+
+ /*
+ * Path to the working directory.
+ * A NULL value indicates that there is no working directory.
+ */
+ char *worktree;
+
+ /* Configurations */
+ /*
+ * Bit used during initialization to indicate if repository state (like
+ * the location of the 'objectdir') should be read from the
+ * environment. By default this bit will be set at the begining of
+ * 'repo_init()' so that all repositories will ignore the environment.
+ * The exception to this is 'the_repository', which doesn't go through
+ * the normal 'repo_init()' process.
+ */
+ unsigned ignore_env:1;
+
+ /* Indicate if a repository has a different 'commondir' from 'gitdir' */
+ unsigned different_commondir:1;
+};
+
+extern struct repository *the_repository;
+
+extern void repo_set_gitdir(struct repository *repo, const char *path);
+extern void repo_set_worktree(struct repository *repo, const char *path);
+extern int repo_init(struct repository *repo, const char *gitdir, const char *worktree);
+extern void repo_clear(struct repository *repo);
+
+#endif /* REPOSITORY_H */