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[PATCH 09/10] set_git_dir: handle feeding gitdir to itself

Ideally we'd free the existing gitdir field before assigning
the new one, to avoid a memory leak. But we can't do so
safely because some callers do the equivalent of:


We can detect that case as a noop, but there are even more
complicated cases like:

  set_git_dir(remove_leading_path(worktree, get_git_dir());

where we really do need to do some work, but the original
string must remain valid.

Rather than put the burden on callers to make a copy of the
string (only to free it later, since we'll make a copy of it
ourselves), let's solve the problem inside set_git_dir(). We
can make a copy of the pointer for the old gitdir, and then
avoid freeing it until after we've made our new copy.

Signed-off-by: Jeff King <peff@xxxxxxxx>
 repository.c | 10 +++-------
 setup.c      |  5 -----
 2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/repository.c b/repository.c
index 52f1821c6b..97c732bd48 100644
--- a/repository.c
+++ b/repository.c
@@ -56,16 +56,12 @@ static void repo_setup_env(struct repository *repo)
 void repo_set_gitdir(struct repository *repo, const char *path)
 	const char *gitfile = read_gitfile(path);
+	char *old_gitdir = repo->gitdir;
-	/*
-	 * 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);
+	free(old_gitdir);
diff --git a/setup.c b/setup.c
index 23950173fc..6d8380acd2 100644
--- a/setup.c
+++ b/setup.c
@@ -399,11 +399,6 @@ void setup_work_tree(void)
 		setenv(GIT_WORK_TREE_ENVIRONMENT, ".", 1);
-	/*
-	 * NEEDSWORK: this call can essentially be set_git_dir(get_git_dir())
-	 * which can cause some problems when trying to free the old value of
-	 * gitdir.
-	 */
 	set_git_dir(remove_leading_path(git_dir, work_tree));
 	initialized = 1;