Restore git-hook commands

Author: schedutron

script/git-hooks/README.md

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+# Git Hooks
+
+This directory contains all Git hooks used in Peloton. Git hooks provide
+a mechanism to execute custom scripts when important events occur during
+your interaction with this Git repository. More details on Git hooks can
+be found [here](https://git-scm.com/book/gr/v2/Customizing-Git-Git-Hooks).
+
+### Pre-commit
+
+A pre-commit hook is fired on every commit into your local Git
+repository. Peloton's pre-commit hook collects all modified files
+(excluding deleted files) and runs them through our source code
+validator script in `script/validator/source_validator.py`. *Ideally*,
+we should also ensure every commit successfully compiles and, to a
+lesser extent, that the commit passes the tests, but this isn't
+reasonable for now.
+
+**Installation:** Under the peloton root directory, run
+`ln -s ../../script/git-hooks/pre-commit .git/hooks/pre-commit` to
+install locally. The pre-commit file should already have executable
+permission, but check again to make sure.

script/git-hooks/pre-commit

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+#!/bin/sh
+# Source validation pre-commit hook
+#
+# This script collects all modified files and runs it through our source code
+# validation script. The validation script returns 0 on success and 1 on any
+# failure.
+#
+# To enable, symlink this file to '.git/hooks/pre-commit' like so:
+#   ln -s ../../script/git-hooks/pre-commit .git/hooks/pre-commit
+
+FORMATTER_COMMAND="./script/formatting/formatter.py"
+
+FILES=$(git diff --name-only HEAD --cached --diff-filter=d | grep '\.\(cpp\|h\)$')
+if [ -n "$FILES" ]; then
+  ./script/validators/source_validator.py --files $FILES
+  RESULT=$?
+  if [ $RESULT -ne 0 ]; then
+    echo "***************************************"
+    echo "******* Peloton Pre-Commit Hook *******"
+    echo "***************************************"
+    echo "Use \"$FORMATTER_COMMAND -c -f\" to format all staged files."
+    echo "Or use \"$FORMATTER_COMMAND --no-verify\" to temporarily bypass the pre-commit hook."
+    echo
+    echo "Be aware that changed files have to be staged again!"
+    echo "***************************************"
+  fi
+  exit $RESULT
+fi
+
+exit 0