From: Junio C Hamano
Subsequent updates to branches always creates new file under $GIT_DIR/refs hierarchy.
+A recommended practice to deal with a repository with too many +refs is to pack its refs with --all --prune once, and +occasionally run git-pack-refs --prune. Tags are by +definition stationary and are not expected to change. Branch +heads will be packed with the initial pack-refs --all, but +only the currently active branch heads will become unpacked, +and next pack-refs (without --all) will leave them +unpacked.
-The command by default packs all tags and leaves branch tips +The command by default packs all tags and refs that are already +packed, and leaves other refs alone. This is because branches are expected to be actively developed and packing their tips does not help performance. This option causes branch tips to be packed as well. Useful for @@ -327,7 +336,7 @@ hierarchy after packing them. This option tells it not to.