Clean up unused checkouts on dev-desktops

User might checkout repositories on the dev-desktops, work on them for a
while, and then move on to other projects. The unused checkouts, in
particular their `build` or `target` directories, can use up a lot of
space that we want to reclaim periodically. A script has been created
that finds all cache directories, checks recursively if any file in
their root directory has been modified within a given time frame, and if
not deletes the cache directory.

Author: jdno

ansible/roles/dev-desktop/files/clean-unused-checkouts.sh

@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+
+# Clean up unused checkouts
+#
+# This script is used to find old checkouts that are no longer in use. Given the
+# size of the build directory, regularly cleaning them up can save significant
+# amounts of disk space.
+
+# Enable strict mode for Bash
+# http://redsymbol.net/articles/unofficial-bash-strict-mode/
+set -euo pipefail
+IFS=$'\n\t'
+
+# Print directories and their size instead of deleting them
+dry_run=false
+
+# Default to search for checkouts older than 60 days
+time="60"
+
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --dry-run)
+      dry_run=true
+      shift # past argument
+      ;;
+    -t|--time)
+      time="${2}"
+      shift # past argument
+      shift # past value
+      ;;
+    -*)
+      echo "Unknown option $1"
+      exit 1
+      ;;
+  esac
+done
+
+# Find all build or target directories created by users
+#
+# This command combines (`-o`) two different conditions to find all build and
+# target directories that users have created. Within each home directory, we
+# recursively look for directories that either have a file named `x.py` and a
+# directory named `build`, or a file named `Cargo.toml` and a directory named
+# `target`.
+all_cache_directories=$(find /home -type d \( -name build -execdir test -f "x.py" \; -o -name target -execdir test -f "Cargo.toml" \; \) -print | sort | uniq)
+
+# For each checkout, we want to determine if the user has been working on it
+# within the `$time` number of days.
+unused_cache_directories=$(for directory in $all_cache_directories; do
+  project=$(dirname "${directory}")
+
+  # Find all directories with files that have been modified less than $time days ago
+  modified=$(find "${project}" -type f -mtime -"${time}" -printf '%h\n' | xargs -r dirname | sort | uniq)
+
+  # If no files have been modified in the last 90 days, then the project is
+  # considered old.
+  if [[ -z "${modified}" ]]; then
+    echo "${directory}"
+  fi
+done)
+
+# Delete the build directories in the unused checkouts
+for directory in $unused_cache_directories; do
+  if [[ "${dry_run}" == true ]]; then
+    du -sh "${directory}"
+  else
+    echo "Deleting ${directory}"
+    rm -rf "${directory}"
+  fi
+done