acid: source: Prevent creation of local branches/refs

Previously (and as is the default behavior in git), when cloning fresh
cache repositories for user services, we would acquire current
remote-tracking branches, tags, and a local branch tracking origin/HEAD.

In practice, this local branch becomes vestigial.  As we fetch updates,
we always checkout by commit hash and leave the repository in a detached
HEAD.  The local branch reference is therefore never updated.  This is
fine for the functionality of ACID.  However, if querying the repo for
information about the current version, it is possible for tools like
`git describe` to describe HEAD in terms of this stale branch ref.

Now, when we clone a repository arrange for there to be no 'local'
branch references.  Only remote-tracking branches and tags.
Remote-tracking branches are properly updated and removed by our fetch
command.  Additionally, prevent the remote 'origin/HEAD' symbolic ref,
since it would be mildly confusing for it to pop up to the user as well.

In effect, we limit our ref namespace only to branches and tags that
actually exist on the remote host.

Signed-off-by: Malfurious <m@lfurio.us>

1 files changed, 15 insertions, 4 deletions

diff --git a/acid/acid-source b/acid/acid-source
index 351d3d0..8c62c44 100755
--- a/acid/acid-source
+++ b/acid/acid-source
@@ -37,13 +37,24 @@ if ! echo "$1" | grep -Eq '^[-_a-z0-9]*$'; then
 fi
 
 if ! [ -d "$1" ]; then
+    # New repository
     git clone "$2" "$1" >&2 || fail
-    touch "$1/.git/previous_hash"
-    touch "$1/.git/previous_slug"
+    cd "$1"
+
+    # Strip down to tags and remote refs only
+    git remote set-head origin --delete >/dev/null 2>&1
+    git checkout HEAD~0 >/dev/null 2>&1
+    git for-each-ref --format='delete %(refname)' refs/heads \
+        | git update-ref --stdin >/dev/null 2>&1
+
+    # Init cyche metadata
+    touch ".git/previous_hash"
+    touch ".git/previous_slug"
+else
+    # Existing repository
+    cd "$1"
 fi
 
-cd "$1"
-
 git remote set-url origin "$2" >&2 # pick up url changes
 git fetch --all --prune >&2 || fail