Some tweaks and add readme

README.md

@@ -1 +1,58 @@
-# docker-repo-scan-action
+# Scan Docker Tags Action
+
+Scan a Docker image repository for recently-updated tags. This is helpful e.g. when your project relies on a certain Docker image and you want to rebuild it every time the base image is updated.
+
+
+## Example
+
+This example workflow scans an image every 15 minutes and prints all tags that were updated since the last run.
+
+```yml
+name: Scan Docker Repo
+on:
+  schedule:
+    - cron: '*/15 * * * *'
+
+jobs:
+  scan:
+    name: List Recent Updates
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Scan Docker Repository
+        uses: dhet/docker-repo-scan-action@v1
+        with:
+          image: mhart/alpine-node
+          max-age-minutes: 15
+          username: ${{ secrets.DOCKER_HUB_USER }}
+          password: ${{ secrets.DOCKER_HUB_PASSWORD }}
+        id: scan
+      - name: Print
+        run: "echo 'Recent updates: ${{ steps.scan.outputs.tags }}'"
+```
+**Output:**
+```
+Recent updates: slim-14.4,slim-14,slim,latest
+```
+
+## Required Inputs
+
+|Parameter|Description
+|---|---
+|`image`|The Docker image to scan (sans tag), e.g. "mhart/alpine-node"
+|`max-age-minutes`|The maximum age of tags to consider. Older tags are discarded. E.g. `30` for 30 minutes
+|`username`|The username used to authenticate against the Docker repository
+|`password`|The password used to authenticate against the Docker repository
+
+
+## Optional Inputs
+|Parameter|Description|Default
+|---|---|---
+|`tag-regex`|A regular expression for filtering tags. Backslashes need to be escaped. E.g. `\\d+\\.\\d+$` matches semver, `latest` matches only the "latest" tag.|`.*`
+|`repo-url`|The URL of the Docker registry. Defaults to Dockerhub.|`https://hub.docker.com`
+
+
+## Outputs
+The only output this action exposes is the `tags` output. `tags` is a comma-separated list of all image tags that have 
+changed in the specified time frame. The list is sorted by date in ascending order. E.g. `v1.0.7,v1.0.8,latest`.

action.yml

@@ -4,6 +4,9 @@ inputs:
   image:
     description: The Docker image to scan (sans tag), e.g. "mhart/alpine-node"
     required: true
+  max-age-minutes:
+    description: The maximum age of tags in minutes. Older tags are discarded
+    required: true
   username:
     description: The username used to authenticate against the Docker repository
     required: true
@@ -16,24 +19,18 @@ inputs:
       semver, `latest` matches only the "latest" tag
     required: false
     default: '.*'
-  max-age-minutes:
-    description: The maximum age of tags in minutes. Older tags are discarded. Defaults to 30 minutes
-    required: false
-    default: '30'
   repo-url:
     description: The URL of the Docker registry. Defaults to Dockerhub (https://hub.docker.com)
     required: false
     default: https://hub.docker.com
-  output-delimiter:
-    description: The delimiter to use for the output. Defaults to ","
-    required: false
-    default: ','
 outputs:
   tags:
-    description: A list of all image tags that have changed in the specified time frame
+    description: >  
+      A comma-separated list of all image tags that have changed in the specified time frame, sorted by date in 
+      ascending order (oldest first)
 runs:
   using: node12
   main: dist/index.js
 branding:
-  icon: rotate-cw
-  color: yellow
+  icon: refresh-cw
+  color: blue

index.js

@@ -2,15 +2,14 @@ const fetch = require("node-fetch")
 const core = require('@actions/core');
 
 
-let repoUrl, image, regex, maxAgeMinutes, outputDelimiter, username, password
+let repoUrl, image, regex, maxAgeMinutes, username, password
 try {
-  repoUrl = core.getInput("repo-url")
-  image = core.getInput("image")
-  regex = new RegExp(core.getInput("tag-regex"))
+  repoUrl       = core.getInput("repo-url")
+  image         = core.getInput("image")
+  regex         = new RegExp(core.getInput("tag-regex"))
   maxAgeMinutes = parseInt(core.getInput("max-age-minutes"))
-  outputDelimiter = core.getInput("output-delimiter")
-  username = core.getInput("username")
-  password = core.getInput("password")
+  username      = core.getInput("username")
+  password      = core.getInput("password")
 } catch (err) {
   const msg = "Failed to initialize action: " + err.message
   core.setFailed(msg)
@@ -41,7 +40,7 @@ fetch(`${repoUrl}/v2/users/login/`, {
     .filter(filterOldEntry)
     .filter(el => regex.test(el.name))
     .map(el => el.name)
-    .join(outputDelimiter)
+    .join(",")
 
   core.setOutput("tags", tags)
 })
@@ -68,7 +67,7 @@ function byDateAsc(a, b) {
 }
 
 function filterOldEntry(entry) {
-  const now = new Date()
+  const now       = new Date()
   const entryDate = new Date(entry.last_updated)
   return (now - entryDate) < maxAgeMinutes * 60 * 1000
 }