add git-ignore-add function to git module

modules/git/README.md

@@ -231,6 +231,7 @@ Functions
   - `git-hub-shorten-url` shortens GitHub URLs.
   - `git-info` exposes repository information via the `$git_info` associative
     array.
+  - `git-ignore-add` adds any passed paramaters to the root's .gitignore.
   - `git-root` displays the path to the working tree root.
   - `git-stash-clear-interactive` asks for confirmation before clearing the stash.
   - `git-stash-dropped` lists dropped stashed states.

modules/git/functions/git-ignore-add

@@ -0,0 +1,17 @@
+#
+# Adds files passed as parameters to .gitignore in project root
+#
+# Authors:
+#   Matt Hamilton <m@tthamilton.com>
+#
+
+# make sure we have a git-root
+if ! git-root &> /dev/null; then
+  print 'not in a git repository' >&2
+  return 1
+fi
+
+# we are in a git repository. add parameters to .gitignore
+for file in "$@" do
+  print "$file" >>! $(git-root)/.gitignore
+done