Handle global expressions (#71)

Co-authored-by: CrazyMax <crazy-max@users.noreply.github.com>

README.md

@@ -38,6 +38,7 @@ ___
   * [`type=sha`](#typesha)
 * [Notes](#notes)
   * [Latest tag](#latest-tag)
+  * [Global expressions](#global-expressions)
   * [Overwrite labels](#overwrite-labels)
 * [Keep up-to-date with GitHub Dependabot](#keep-up-to-date-with-github-dependabot)
 * [Contributing](#contributing)
@@ -554,6 +555,25 @@ tags: |
 * [`type=semver,pattern=...`](#typesemver)
 * [`type=match,pattern=...`](#typematch)
 
+### Global expressions
+
+The following [Handlebars template](https://handlebarsjs.com/guide/) expressions for `prefix`, `suffix` and `value`
+attributes are available:
+
+| Expression               | Output               |
+|--------------------------|----------------------|
+| `{{branch}}`             | `master`             |
+| `{{tag}}`                | `v1.2.3`             |
+| `{{sha}}`                | `90dd603`            |
+
+```yaml
+tags: |
+  # dynamically set the branch name as a prefix
+  type=sha,prefix={{branch}}-
+  # dynamically set the branch name and sha as a custom tag
+  type=raw,value=mytag-{{branch}}-{{sha}}
+```
+
 ### Overwrite labels
 
 If some of the [OCI Image Format Specification](https://github.com/opencontainers/image-spec/blob/master/annotations.md)

__tests__/meta.test.ts

@@ -89,7 +89,8 @@ describe('null', () => {
       {
         images: ['user/app'],
         tags: [
-          `type=sha`
+          `type=sha`,
+          `type=raw,{{branch}}`,
         ]
       } as Inputs,
       {
@@ -586,6 +587,36 @@ describe('push', () => {
         "org.opencontainers.image.revision=90dd6032fac8bda1b6c4436a2e65de27961ed071",
         "org.opencontainers.image.licenses=MIT"
       ]
+    ],
+    [
+      'push17',
+      'event_push_defbranch.env',
+      {
+        images: ['user/app'],
+        tags: [
+          `type=raw,value=mytag-{{branch}}`,
+          `type=raw,value=mytag-{{tag}}`
+        ],
+      } as Inputs,
+      {
+        main: 'mytag-master',
+        partial: ['mytag-'],
+        latest: false
+      } as Version,
+      [
+        'user/app:mytag-master',
+        'user/app:mytag-'
+      ],
+      [
+        "org.opencontainers.image.title=Hello-World",
+        "org.opencontainers.image.description=This your first repo!",
+        "org.opencontainers.image.url=https://github.com/octocat/Hello-World",
+        "org.opencontainers.image.source=https://github.com/octocat/Hello-World",
+        "org.opencontainers.image.version=mytag-master",
+        "org.opencontainers.image.created=2020-01-10T00:30:00.000Z",
+        "org.opencontainers.image.revision=90dd6032fac8bda1b6c4436a2e65de27961ed071",
+        "org.opencontainers.image.licenses=MIT"
+      ]
     ]
   ])('given %p with %p event', tagsLabelsTest);
 });
@@ -1210,6 +1241,35 @@ describe('tag', () => {
         "org.opencontainers.image.revision=90dd6032fac8bda1b6c4436a2e65de27961ed071",
         "org.opencontainers.image.licenses=MIT"
       ]
+    ],
+    [
+      'tag20',
+      'event_tag_v1.1.1.env',
+      {
+        images: ['org/app', 'ghcr.io/user/app'],
+        tags: [
+          `type=raw,{{tag}}-{{sha}}-foo`
+        ]
+      } as Inputs,
+      {
+        main: 'v1.1.1-90dd603-foo',
+        partial: [],
+        latest: false
+      } as Version,
+      [
+        'org/app:v1.1.1-90dd603-foo',
+        'ghcr.io/user/app:v1.1.1-90dd603-foo'
+      ],
+      [
+        "org.opencontainers.image.title=Hello-World",
+        "org.opencontainers.image.description=This your first repo!",
+        "org.opencontainers.image.url=https://github.com/octocat/Hello-World",
+        "org.opencontainers.image.source=https://github.com/octocat/Hello-World",
+        "org.opencontainers.image.version=v1.1.1-90dd603-foo",
+        "org.opencontainers.image.created=2020-01-10T00:30:00.000Z",
+        "org.opencontainers.image.revision=90dd6032fac8bda1b6c4436a2e65de27961ed071",
+        "org.opencontainers.image.licenses=MIT"
+      ]
     ]
   ])('given %p with %p event', tagsLabelsTest);
 });