Optimize fetch-git.

tests/jobs/git-update.sh

@@ -0,0 +1,26 @@
+#! /bin/sh
+
+cd "$1"
+STATE_FILE=.state
+if test -e $STATE_FILE; then
+    state=$(cat $STATE_FILE)
+else
+    state=0;
+fi
+
+case $state in
+    (0)
+    echo "Add new file."
+    touch git-file-2
+    git add git-file-2 >&2
+    git commit -m "add git file 2" git-file-2 >&2
+    ;;
+    (1)
+    echo "Rewrite commit."
+    echo 1 > git-file-2
+    git add git-file-2 >&2
+    git commit --amend -m "add git file 2" git-file-2 >&2
+    ;;
+esac
+
+echo $(($state + 1)) > $STATE_FILE