Index: commit-id
===================================================================
--- 6ad600e20c89323c1d3049f75b8ca9b0a2d72167/commit-id  (mode:100755 sha1:4efcb6bdfdb2b2c5744f5d4d47d92beb7777ed59)
+++ uncommitted/commit-id  (mode:100775)
@@ -9,22 +9,30 @@
 SHA1ONLY="^$SHA1$"
 
 id=$1
+
 if [ ! "$id" ] || [ "$id" = "this" ] || [ "$id" = "HEAD" ]; then
 	id=$(cat .git/HEAD)
-fi
 
-if (echo $id | egrep -vq "$SHA1ONLY") && [ -r ".git/refs/tags/$id" ]; then
+elif [ -r ".git/refs/tags/$id" ]; then
 	id=$(cat ".git/refs/tags/$id")
-fi
 
-if (echo $id | egrep -vq "$SHA1ONLY") && [ -r ".git/refs/heads/$id" ]; then
+elif [ -r ".git/refs/heads/$id" ]; then
 	id=$(cat ".git/refs/heads/$id")
-fi
 
-idpref=$(echo "$id" | cut -c -2)
-idpost=$(echo "$id" | cut -c 3-)
-if [ $(find ".git/objects/$idpref" -name "$idpost*" 2>/dev/null | wc -l) -eq 1 ]; then
-	id=$idpref$(basename $(echo .git/objects/$idpref/$idpost*))
+# Short id's must be lower case and at least 4 digits.
+elif [[ "$id" == [0-9a-z][0-9a-z][0-9a-z][0-9a-z]* ]]; then
+	idpost=${id#??}
+	idpref=${id%$idpost}
+
+	# Assign array elements to matching names
+	idmatch=($(echo .git/objects/$idpref/$idpost*))
+
+	if [ ${#idmatch[*]} -eq 1 ] && [ -r "$idmatch" ]; then
+		id=$idpref${idmatch#.git/objects/$idpref/}
+	elif [ ${#idmatch[*]} -gt 1 ]; then
+		echo "Ambiguous id: $id" >&2
+		exit 1
+	fi
 fi
 
 if echo $id | egrep -vq "$SHA1ONLY"; then
Index: tree-id
===================================================================
--- 6ad600e20c89323c1d3049f75b8ca9b0a2d72167/tree-id  (mode:100755 sha1:1495ff78af71b57e21653512932bcda88fe05454)
+++ uncommitted/tree-id  (mode:100775)
@@ -7,8 +7,35 @@
 
 SHA1="[A-Za-z0-9]{40}"
 TREE="^tree $SHA1$"
+SHA1ONLY="^$SHA1$"
 
-id=$(cat-file commit $(commit-id "$1") | egrep "$TREE" | cut -d ' ' -f 2)
+id=$1
+
+# Is it a commit?
+commit=$(commit-id $id 2>/dev/null)
+if [ "$commit" ]; then
+	id=$(cat-file commit "$commit") | egrep "$TREE" | cut -d ' ' -f 2)
+
+# Short id's must be lower case and at least 4 digits.
+elif [[ "$id" == [0-9a-z][0-9a-z][0-9a-z][0-9a-z]* ]]; then
+	idpost=${id#??}
+	idpref=${id%$idpost}
+
+	# Assign array elements to matching names
+	idmatch=($(echo .git/objects/$idpref/$idpost*))
+
+	if [ ${#idmatch[*]} -eq 1 ] && [ -r "$idmatch" ]; then
+		id=$idpref${idmatch#.git/objects/$idpref/}
+	elif [ ${#idmatch[*]} -gt 1 ]; then
+		echo "Ambiguous id: $id" >&2
+		exit 1
+	fi
+fi
+
+if echo $id | egrep -vq "$SHA1ONLY"; then
+	echo "Invalid id: $id" >&2
+	exit 1
+fi
 
 if [ "$(cat-file -t "$id")" != "tree" ]; then
 	echo "Invalid id: $id" >&2
Index: parent-id
===================================================================
--- 6ad600e20c89323c1d3049f75b8ca9b0a2d72167/parent-id  (mode:100755 sha1:f35877a6aa5b68d2fb4a388dcfa9b3e64262604e)
+++ uncommitted/parent-id  (mode:100775)
@@ -5,7 +5,8 @@
 #
 # Takes ID of the current commit, defaults to HEAD.
 
-PARENT="^parent [A-Za-z0-9]{40}$"
+SHA1="[A-Za-z0-9]{40}"
+PARENT="^parent $SHA1$"
 
 id=$(commit-id $1) || exit 1