bugfix: Check the mirror existence while holding the mirror lock

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Upcoming version
 
+- Bugfix: Check the existence of a mirror while holding the mirror lock to no longer delete a mirror that was
+  created by a concurrent gitcache process.
 - Bugfix: Fetch the LFS objects of a `git checkout` of a tag or a commit as well. Previously, only a checkout of a
   branch triggered an LFS fetch of the mirror and the LFS objects of a tag or commit were downloaded by the git-lfs
   filters of the checkout itself.

src/git_cache/git_mirror.py

@@ -166,10 +166,9 @@ def update(self, ref=None, force=False):
         Return:
             Returns True if the mirror was updated or False if the request timed out.
         """
-        mirror_exists = self.database.get(self.path) is not None
         try:
             with Locker(f"Mirror {self.path}", self.lockfile, self.config):
-                if not mirror_exists:
+                if self.database.get(self.path) is None:
                     rmtree(self.path, ignore_errors=True)
                     if self._clone(ref):
                         record_cache("miss_create", self.path)
@@ -202,10 +201,9 @@ def ensure_exists(self, ref=None) -> bool:
         Return:
             Returns True if the mirror exists now or False if the request timed out.
         """
-        mirror_exists = self.database.get(self.path) is not None
         try:
             with Locker(f"Mirror {self.path}", self.lockfile, self.config):
-                if not mirror_exists:
+                if self.database.get(self.path) is None:
                     rmtree(self.path, ignore_errors=True)
                     if self._clone(ref):
                         record_cache("miss_create", self.path)
@@ -227,10 +225,9 @@ def fetch(self, command_args: List[str]) -> bool:
         Return:
             Returns True if the command was successfull, otherwise False.
         """
-        mirror_exists = self.database.get(self.path) is not None
         try:
             with Locker(f"Mirror {self.path}", self.lockfile, self.config):
-                if not mirror_exists:
+                if self.database.get(self.path) is None:
                     LOG.error("Mirror does not exist!")
                     return False
                 return self._fetch(command_args)