diff --git a/commit b/commit
new file mode 100755
index 0000000..90ae53b
--- /dev/null
+++ b/commit
@@ -0,0 +1,10 @@
+#!/bin/bash -e
+
+# TODO unless this is the initial commit
+parents='-p HEAD'
+echo '# write a commit message' > .zit/COMMIT_EDITMSG
+vi .zit/COMMIT_EDITMSG
+tree=$(./write-tree)
+commit=$(grep -v '^#' .zit/COMMIT_EDITMSG | ./commit-tree $tree $parents)
+./update-ref HEAD $commit
+rm -f .zit/COMMIT_EDITMSG
diff --git a/commit-tree b/commit-tree
index b102b4b..3551f62 100755
--- a/commit-tree
+++ b/commit-tree
@@ -3,7 +3,8 @@
 echo tree $1 > .zit/commit.tmp
 shift
 while [[ $1 == -p ]]; do
-    echo parent $2 >> .zit/commit.tmp
+    parent=$(./rev-parse $2)
+    echo parent $parent >> .zit/commit.tmp
     shift; shift
 done
 echo author "Joe Mou <joe@mou.fo> $(date +'%s %z')" >> .zit/commit.tmp
diff --git a/rev-parse b/rev-parse
new file mode 100755
index 0000000..11ff61f
--- /dev/null
+++ b/rev-parse
@@ -0,0 +1,13 @@
+#!/bin/bash -e
+# only implements --verify
+
+# sha1_name.c:get_sha1
+
+if [[ ${#1} -eq 40 ]]; then
+    echo $1
+else
+    cat .zit/$(./symbolic-ref $1) 2> /dev/null || \
+        cat .zit/$(./symbolic-ref refs/$1) 2> /dev/null || \
+        cat .zit/$(./symbolic-ref refs/tags/$1) 2> /dev/null || \
+        cat .zit/$(./symbolic-ref refs/heads/$1)
+fi
diff --git a/symbolic-ref b/symbolic-ref
new file mode 100755
index 0000000..9a72285
--- /dev/null
+++ b/symbolic-ref
@@ -0,0 +1,8 @@
+#!/bin/bash -e
+
+# refs.c:resolve_ref
+path=.zit/$1
+while grep -q '^ref: ' $path 2> /dev/null; do
+    path=.zit/$(cut -d' ' -f2 < $path)
+done
+echo $path | cut -d/ -f2-
diff --git a/update-ref b/update-ref
new file mode 100755
index 0000000..c217c1b
--- /dev/null
+++ b/update-ref
@@ -0,0 +1,7 @@
+#!/bin/bash -e
+
+path=.zit/$(./symbolic-ref $1)
+sha1=$(./rev-parse $2)
+# TODO initialize directory structure instead?
+mkdir -p $(dirname $path)
+echo $sha1 > $path