random

... because readlink has a better chance of being installed.

.travis.yml

@@ -5,4 +5,4 @@ install:
  - go get github.com/constabulary/gb/...
  - go get github.com/golang/lint/golint
  - go get github.com/fzipp/gocyclo
-script: ./hooks/pre-commit
+script: bash -x ./hooks/pre-commit

hooks/pre-commit

@@ -1,9 +1,44 @@
-#! /bin/bash
+#!/bin/bash
 
 set -eu
 
+# make the GIT_DIR and GIT_INDEX_FILE absolute, before we change dir
+export GIT_DIR=$(readlink -f `git rev-parse --git-dir`)
+if [ -n "${GIT_INDEX_FILE:+x}" ]; then
+    export GIT_INDEX_FILE=$(readlink -f "$GIT_INDEX_FILE")
+fi
+
+wd=`pwd`
+
+# create a temp dir. The `trap` incantaion will ensure that it is removed again
+# when this script completes.
+tmpdir=`mktemp -d`
+trap 'rm -rf "$tmpdir"' EXIT
+cd "$tmpdir"
+
+# get a copy of the index
+git checkout-index -a
+
+# run our checks
 golint src/...
 go fmt ./src/...
 go tool vet --shadow ./src
 gocyclo -over 12 src/
 gb test
+
+# if there are no changes from the index, we are done
+git diff --quiet && exit 0
+
+# we now need to apply any changes made to both the index and the working copy.
+# so, first get a patch
+git diff > "$GIT_DIR/pre-commit.patch"
+
+# add the changes to the index
+git add -u
+
+# attempt to apply the changes to the wc (but don't fail the commit for it if
+# there are conflicts).
+cd "$wd"
+git apply "$GIT_DIR/pre-commit.patch" 2>/dev/null &&
+    rm "$GIT_DIR/pre-commit.patch" ||
+    echo "warning: unable to apply changes from commit hook to working copy; patch is in $GIT_DIR/pre-commit.patch" >&2