From a89cb1db1fdc03540d0cbc8e72dd3e05b9f11712 Mon Sep 17 00:00:00 2001
From: Marcel <msc@vesoma.com>
Date: Thu, 10 Sep 2026 16:22:23 +0200
Subject: [PATCH] bugfix: Fetch the LFS objects of a checkout of a tag or
 commit

The refs given to a git checkout command were resolved with 'git show-ref'
and an LFS fetch of the mirror was performed only if the ref was found as a
remote branch. Therefore, a checkout of a tag or a commit did not fetch the
LFS objects into the mirror and the git-lfs filters of the checkout had to
download them on their own.

The refs are now resolved to commits and are checked against the mirror, so
that a checkout of a tag or a commit fetches the LFS objects as well.

Co-authored-by: Cursor <cursoragent@cursor.com>
---
 CHANGELOG.md                              |  4 ++++
 src/git_cache/commands/checkout.py        | 27 ++++++++++++-----------
 src/git_cache/git_mirror.py               | 13 +++++++++++
 test/functional_tests/test_16_checkout.py |  6 +++++
 4 files changed, 37 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index be77f67..56d5126 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Upcoming version
 
+- 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.
+
 ## v1.0.34
 
 - Feature: Add optional detail and summary log files controlled by `GITCACHE_DETAIL_LOG` and `GITCACHE_SUMMARY_LOG` for CI-friendly invocation tracing. (thanks to ditschi)
diff --git a/src/git_cache/commands/checkout.py b/src/git_cache/commands/checkout.py
index 0814b48..84669e2 100644
--- a/src/git_cache/commands/checkout.py
+++ b/src/git_cache/commands/checkout.py
@@ -43,23 +43,24 @@ def git_checkout(git_options: GitOptions) -> int:
         Returns 0 on success, otherwise the return code of the last failed
         command.
     """
-    # Collect all refs for an lfs fetch
+    mirror_url = get_mirror_url(git_options)
+    if mirror_url is None:
+        return simple_call_command(git_options.get_real_git_all_args())
+
+    mirror = GitMirror(url=mirror_url, database=Database())
+
+    # Collect all commits for an lfs fetch
     ref_candidates = [x for x in git_options.command_args if not x.startswith("-") and not x.startswith(":")]
     lfs_fetch_refs = []
     for ref in ref_candidates:
         command = git_options.get_real_git_with_options()
-        command += ["show-ref", ref]
-        retval, output = getstatusoutput(command)
-        if retval == 0 and "remotes" in output:
-            lfs_fetch_refs.append(ref)
-
-    if lfs_fetch_refs:
-        mirror_url = get_mirror_url(git_options)
-        if mirror_url:
-            database = Database()
-            mirror = GitMirror(url=mirror_url, database=database)
-            for ref in lfs_fetch_refs:
-                mirror.fetch_lfs(ref)
+        command += ["rev-parse", "--verify", "--quiet", f"{ref}^{{commit}}"]
+        retval, commit = getstatusoutput(command)
+        if retval == 0 and mirror.has_commit(commit):
+            lfs_fetch_refs.append(commit)
+
+    for ref in lfs_fetch_refs:
+        mirror.fetch_lfs(ref)
 
     return simple_call_command(git_options.get_real_git_all_args())
 
diff --git a/src/git_cache/git_mirror.py b/src/git_cache/git_mirror.py
index 88d297d..93d25e9 100644
--- a/src/git_cache/git_mirror.py
+++ b/src/git_cache/git_mirror.py
@@ -265,6 +265,19 @@ def fetch_lfs(self, ref=None, options=None):
         LOG.warning("LFS fetch skipped as git-lfs is not available on this system!")
         return True
 
+    def has_commit(self, commit: str) -> bool:
+        """Check whether the given commit is part of the mirror.
+
+        Args:
+            commit (str): The commit to search for.
+
+        Return:
+            Returns True if the mirror contains the given commit.
+        """
+        command = [self.config.get("System", "RealGit"), "cat-file", "-e", f"{commit}^{{commit}}"]
+        return_code, _ = getstatusoutput(command, cwd=self.git_dir)
+        return return_code == 0
+
     def cleanup(self):
         """Delete the mirror if it is too old.
 
diff --git a/test/functional_tests/test_16_checkout.py b/test/functional_tests/test_16_checkout.py
index a920c9f..d8de681 100644
--- a/test/functional_tests/test_16_checkout.py
+++ b/test/functional_tests/test_16_checkout.py
@@ -49,6 +49,12 @@ def test_checkout(gitcache_ifc: GitcacheIfc):
     )
     assert os.path.exists(lfs_obj_file)
 
+    # Checkout of a commit should fetch the lfs files as well
+    commit = gitcache_ifc.run_ok(["git", "-C", checkout, "rev-parse", "extra_branch"]).stdout.strip()
+    lfs_updates = gitcache_ifc.db_field("lfs-updates", repo)
+    gitcache_ifc.run_ok(["git", "-C", checkout, "checkout", commit])
+    assert lfs_updates + 1 == gitcache_ifc.db_field("lfs-updates", repo)
+
 
 # ----------------------------------------------------------------------------
 #  EOF