Add default git pre-commit hook for all repos

oscar/configuration.nix

@@ -145,6 +145,9 @@
         "\\#*\\#"
         "venv"
       ];
+      hooks = {
+        pre-commit = ./git-pre-commit-hook;
+      };
       signing.signByDefault = true;
       signing.key = null; # "let GnuPG decide what signing key to use depending on commit's author"
     };

oscar/git-pre-commit-hook

@@ -0,0 +1,40 @@
+if git rev-parse --verify HEAD >/dev/null 2>&1
+then
+        against=HEAD
+else
+        # Initial commit: diff against an empty tree object
+        against=$(git hash-object -t tree /dev/null)
+fi
+
+# If you want to allow non-ASCII filenames set this variable to true.
+allownonascii=$(git config --type=bool hooks.allownonascii)
+
+# Redirect output to stderr.
+exec 1>&2
+
+# Cross platform projects tend to avoid non-ASCII filenames; prevent
+# them from being added to the repository. We exploit the fact that the
+# printable range starts at the space character and ends with tilde.
+if [ "$allownonascii" != "true" ] &&
+        # Note that the use of brackets around a tr range is ok here, (it's
+        # even required, for portability to Solaris 10's /usr/bin/tr), since
+        # the square bracket bytes happen to fall in the designated range.
+        test $(git diff-index --cached --name-only --diff-filter=A -z $against |
+          LC_ALL=C tr -d '[ -~]\0' | wc -c) != 0
+then
+        cat <<\EOF
+Error: Attempt to add a non-ASCII file name.
+
+This can cause problems if you want to work with people on other platforms.
+
+To be portable it is advisable to rename the file.
+
+If you know what you are doing you can disable this check using:
+
+  git config hooks.allownonascii true
+EOF
+        exit 1
+fi
+
+# If there are whitespace errors, print the offending file names and fail.
+exec git diff-index --check --cached $against --