support semver in manifest [ci skip]

docker/manifest.tmpl

@@ -1,42 +1,48 @@
-image: drone/git:latest
+image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}{{else}}latest{{/if}}
+{{#if build.tags}}
+tags:
+{{#each build.tags}}
+  - {{this}}
+{{/each}}
+{{/if}}
 manifests:
   -
-    image: drone/git:linux-amd64
+    image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}-{{/if}}linux-amd64
     platform:
       architecture: amd64
       os: linux
   -
-    image: drone/git:linux-arm64
+    image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}-{{/if}}linux-arm64
     platform:
       variant: v8
       architecture: arm64
       os: linux
   -
-    image: drone/git:linux-arm
+    image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}-{{/if}}linux-arm
     platform:
       variant: v7
       architecture: arm
       os: linux
   -
-    image: drone/git:linux-arm
+    image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}-{{/if}}linux-arm
     platform:
       variant: v6
       architecture: arm
       os: linux
   -
-    image: drone/git:windows-1803-amd64
+    image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}-{{/if}}windows-1803-amd64
     platform:
       architecture: amd64
       os: windows
       version: 1803
   -
-    image: drone/git:windows-1809-amd64
+    image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}-{{/if}}windows-1809-amd64
     platform:
       architecture: amd64
       os: windows
       version: 1809
   -
-    image: drone/git:windows-1903-amd64
+    image: drone/git:{{#if build.tag}}{{trimPrefix "v" build.tag}}-{{/if}}windows-1903-amd64
     platform:
       architecture: amd64
       os: windows