Subject: Re: [PATCH] optionally disable overwriting of ignored files

From: Clemens Buchacher <[email-masked]>
Date: Sat, 21 Aug 2010 15:23:56 +0200

On Fri, Aug 20, 2010 at 01:35:32PM -0700, Junio C Hamano wrote:
>
>     $ echo foo >po
>     $ git checkout pu
> 
> should error out, as "po" is a directory that has tracked contents, and we
> never said the untracked regular file "po" is trashable, but the above
> sequence happily checks the branch out.

Looks like this case is simply overlooked in verify_absent_1(). The
following takes the existing lstat_cache() code and deals with the
FL_ERR case, which is when there is a file in the way of the
leading path.

The patch below fixes the issue and passes the test suite, but it's
lacking in various ways and I am probably breaking something in
lstat_cache(), which I do not completely understand yet.

So it's going to take some more work to fix this properly.

Clemens

 cache.h        |    1 +
 symlinks.c     |   20 ++++++++++++++++++--
 unpack-trees.c |   25 ++++++++++++++++++++++++-
 3 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/cache.h b/cache.h
index dd1b8f7..5a8a99d 100644
--- a/cache.h
+++ b/cache.h
@@ -850,6 +850,7 @@ struct cache_def {
 extern int has_symlink_leading_path(const char *name, int len);
 extern int threaded_has_symlink_leading_path(struct cache_def *, const char *, int);
 extern int has_symlink_or_noent_leading_path(const char *name, int len);
+extern int find_leading_path(const char *name, int len, const char **path, int *path_len);
 extern int has_dirs_only_path(const char *name, int len, int prefix_len);
 extern void schedule_dir_for_removal(const char *name, int len);
 extern void remove_scheduled_dirs(void);
diff --git a/symlinks.c b/symlinks.c
index 8860120..3f78168 100644
--- a/symlinks.c
+++ b/symlinks.c
@@ -152,7 +152,7 @@ static int lstat_cache(struct cache_def *cache, const char *name, int len,
 	 * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
 	 * for the moment!
 	 */
-	save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
+	save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK|FL_ERR);
 	if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
 		cache->path[last_slash] = '\0';
 		cache->len = last_slash;
@@ -199,7 +199,7 @@ int has_symlink_leading_path(const char *name, int len)
 
 /*
  * Return non-zero if path 'name' has a leading symlink component or
- * if some leading path component does not exists.
+ * if some leading path component does not exist.
  */
 int has_symlink_or_noent_leading_path(const char *name, int len)
 {
@@ -210,6 +210,22 @@ int has_symlink_or_noent_leading_path(const char *name, int len)
 }
 
 /*
+ * Stat for leading path.
+ */
+int find_leading_path(const char *name, int len, const char **path, int *path_len)
+{
+	struct cache_def *cache = &default_cache;	/* FIXME */
+	int flags = lstat_cache(cache, name, len,
+			   FL_SYMLINK|FL_NOENT|FL_DIR|FL_ERR, USE_ONLY_LSTAT);
+	*path = cache->path;
+	*path_len = cache->len;
+	if (flags & FL_ERR)
+		return -1;
+	else
+		return flags & (FL_SYMLINK|FL_NOENT);
+}
+
+/*
  * Return non-zero if all path components of 'name' exists as a
  * directory.  If prefix_len > 0, we will test with the stat()
  * function instead of the lstat() function for a prefix length of
diff --git a/unpack-trees.c b/unpack-trees.c
index 8cf0da3..250ed7c 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -1016,12 +1016,35 @@ static int verify_absent_1(struct cache_entry *ce, const char *action,
 				 const char *error_msg)
 {
 	struct stat st;
+	const char *path;
+	int path_len;
+	int ret;
 
 	if (o->index_only || o->reset || !o->update)
 		return 0;
 
-	if (has_symlink_or_noent_leading_path(ce->name, ce_namelen(ce)))
+	ret = find_leading_path(ce->name, ce_namelen(ce), &path, &path_len);
+	if (ret > 0)
 		return 0;
+	else if (ret < 0) {
+		struct cache_entry *result;
+
+		/* FIXME: respect ignores etc. as below */
+
+		/*
+		 * The previous round may already have decided to
+		 * delete this path, which is in a subdirectory that
+		 * is being replaced with a blob.
+		 */
+		result = index_name_exists(&o->result, path, path_len, 0);
+		if (result) {
+			if (result->ce_flags & CE_REMOVE)
+				return 0;
+		}
+
+		return o->gently ? -1 :
+			error(ERRORMSG(o, would_lose_untracked), path, action);
+	}
 
 	if (!lstat(ce->name, &st)) {
 		int dtype = ce_to_dtype(ce);
-- 
1.7.2.1.1.g202c