Add option to control cache key (folder). Fixes #12 and #13

DOCS.md

@@ -7,6 +7,7 @@ The following parameters are used to configure the plugin:
 - **rebuild** - instruct plugin to rebuild cache, can be `true` or `false`
 - **mount** - list of folders or files to cache
 - **ttl** - maximum cache lifetime in days
+- **cache_key** - list of environment variables to use for constructing the cache path
 
 ## Examples
 ```yaml
@@ -55,6 +56,28 @@ pipeline:
 
 The example above shows a situation where cached items older than 7 days will not be restored (they will be removed instead). Only the restore step needs the `ttl` parameter.
 
+## Using the cache_key option
+By default, this plugin uses the repo owner, repo name, and job number to construct a cache key. Say the repository owner is `foo`, the repository name is `bar`, and the job number is `1`,
+the cache key (folder) the plugin will use for the build will be `foo/bar/1`.
+If this is not optimal for your specific situation, it is possible to modify the cache key. For example, let's say that your project differs quite a bit between different branches, you may want to include the branch somewhere in the cache key:
+
+```yaml
+pipeline:
+  restore-cache:
+    image: drillster/drone-volume-cache
+    restore: true
+    mount:
+      - ./node_modules
+    # Mount the cache volume, needs "Trusted"
+    volumes:
+      - /tmp/cache:/cache
+    cache_key: [ DRONE_REPO_OWNER, DRONE_REPO_NAME, DRONE_BRANCH, DRONE_JOB_NUMBER ]
+```
+
+This would lead to the following cache key if a build is triggered for the master branch (and the rest of the situation is the same as the example illustrated above): `foo/bar/master/1`.
+
+In theory you could even use this to share cache between different projects, but extreme caution is advised doing so.
+
 ## Clearing Cache
 Should you want to clear the cache for a project, you can do so by including `[CLEAR CACHE]` in the commit message. The entire cache folder for the project will be cleared before it is restored. The rebuilding of cache will proceed as normal.
 

cacher.sh

@@ -19,32 +19,49 @@ if [[ $DRONE_COMMIT_MESSAGE == *"[NO CACHE]"* ]]; then
     exit 0
 fi
 
+CACHE_PATH="$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER"
+if [[ -n "$PLUGIN_CACHE_KEY" ]]; then
+    function join_by { local IFS="$1"; shift; echo "$*"; }
+    IFS=','; read -ra CACHE_PATH_VARS <<< "$PLUGIN_CACHE_KEY"
+    CACHE_PATH_VALUES=()
+    for env_var in "${CACHE_PATH_VARS[@]}"; do
+        env_var_value="${!env_var}"
+        
+        if [[ -z "$env_var_value" ]]; then
+            echo "Warning! Environment variable '${env_var}' does not contain a value, it will be ignored!"
+        else
+            CACHE_PATH_VALUES+=("${env_var_value}")
+        fi
+    done
+    CACHE_PATH=$(join_by / "${CACHE_PATH_VALUES[@]}")
+fi
+
 IFS=','; read -ra SOURCES <<< "$PLUGIN_MOUNT"
 if [[ -n "$PLUGIN_REBUILD" && "$PLUGIN_REBUILD" == "true" ]]; then
     # Create cache
     for source in "${SOURCES[@]}"; do
         if [ -d "$source" ]; then
             echo "Rebuilding cache for folder $source..."
-            mkdir -p "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source" && \
-                rsync -aHA --delete "$source/" "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source"
+            mkdir -p "/cache/$CACHE_PATH/$source" && \
+                rsync -aHA --delete "$source/" "/cache/$CACHE_PATH/$source"
         elif [ -f "$source" ]; then
             echo "Rebuilding cache for file $source..."
             source_dir=$(dirname $source)
-            mkdir -p "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source_dir" && \
-                rsync -aHA --delete "$source" "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source_dir/"
+            mkdir -p "/cache/$CACHE_PATH/$source_dir" && \
+                rsync -aHA --delete "$source" "/cache/$CACHE_PATH/$source_dir/"
         else
             echo "$source does not exist, removing from cached folder..."
-            rm -rf "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source"
+            rm -rf "/cache/$CACHE_PATH/$source"
         fi
     done
 elif [[ -n "$PLUGIN_RESTORE" && "$PLUGIN_RESTORE" == "true" ]]; then
     # Remove files older than TTL
     if [[ -n "$PLUGIN_TTL" && "$PLUGIN_TTL" > "0" ]]; then
         if [[ $PLUGIN_TTL =~ ^[0-9]+$ ]]; then
-            if [ -d "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER" ]; then
+            if [ -d "/cache/$CACHE_PATH" ]; then
               echo "Removing files and (empty) folders older than $PLUGIN_TTL days..."
-              find "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER" -type f -ctime +$PLUGIN_TTL -delete
-              find "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER" -type d -ctime +$PLUGIN_TTL -empty -delete
+              find "/cache/$CACHE_PATH" -type f -ctime +$PLUGIN_TTL -delete
+              find "/cache/$CACHE_PATH" -type d -ctime +$PLUGIN_TTL -empty -delete
             fi
         else
             echo "Invalid value for ttl, please enter a positive integer. Plugin will ignore ttl."
@@ -52,15 +69,15 @@ elif [[ -n "$PLUGIN_RESTORE" && "$PLUGIN_RESTORE" == "true" ]]; then
     fi
     # Restore from cache
     for source in "${SOURCES[@]}"; do
-        if [ -d "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source" ]; then
+        if [ -d "/cache/$CACHE_PATH/$source" ]; then
             echo "Restoring cache for folder $source..."
             mkdir -p "$source" && \
-                rsync -aHA --delete "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source/" "$source"
-        elif [ -f "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source" ]; then
+                rsync -aHA --delete "/cache/$CACHE_PATH/$source/" "$source"
+        elif [ -f "/cache/$CACHE_PATH/$source" ]; then
             echo "Restoring cache for file $source..."
             source_dir=$(dirname $source)
             mkdir -p "$source_dir" && \
-                rsync -aHA --delete "/cache/$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$DRONE_JOB_NUMBER/$source" "$source_dir/"
+                rsync -aHA --delete "/cache/$CACHE_PATH/$source" "$source_dir/"
         else
             echo "No cache for $source"
         fi