feat(short_sha): add a shortened sha commit id

README.md

@@ -9,6 +9,9 @@ This action slug and expose some github variables.
 - remove leading and trailing `-` caracter,
 - limit the string size to 63 caracters.
 
+Others `Slug`-ish commands are available:
+- `Short SHA` a variable will limit the string size to 8 caracters.
+
 ## Environment Variables
 
 | GitHub environment variable | Slug variable |
@@ -17,6 +20,10 @@ This action slug and expose some github variables.
 | GITHUB_HEAD_REF | GITHUB_HEAD_REF_SLUG |
 | GITHUB_BASE_REF | GITHUB_BASE_REF_SLUG |
 
+| GitHub environment variable | Short variable |
+| - | - |
+| GITHUB_SHA | GITHUB_SHA_SHORT |
+
 ## Example usage
 
 ```yaml
@@ -26,4 +33,5 @@ This action slug and expose some github variables.
     echo ${{ env.GITHUB_REF_SLUG }}
     echo ${{ env.GITHUB_HEAD_REF_SLUG }}
     echo ${{ env.GITHUB_BASE_REF_SLUG }}
+    echo ${{ env.GITHUB_SHA_SHORT }}
 ```

entrypoint.sh

@@ -7,6 +7,12 @@ slug_ref() {
          | cut -c1-63
 }
 
+short_sha(){
+  echo "$1" \
+        | cut -c1-8
+}
+
 echo ::set-env name=GITHUB_REF_SLUG::"$(slug_ref "$GITHUB_REF")"
 echo ::set-env name=GITHUB_HEAD_REF_SLUG::"$(slug_ref "$GITHUB_HEAD_REF")"
 echo ::set-env name=GITHUB_BASE_REF_SLUG::"$(slug_ref "$GITHUB_BASE_REF")"
+echo ::set-env name=GITHUB_SHA_SHORT::"$(short_sha "$GITHUB_SHA")"

tests/short_sha.bats

@@ -0,0 +1,19 @@
+#!/usr/bin/env bats
+
+@test "Short long hash" {
+  test_short_sha \
+    "a35a1a486a260cfd99c5b6f8c6034a2929ba9b3f" \
+    "a35a1a48"
+}
+
+# Load sluf_ref function
+source entrypoint.sh > /dev/null 2>&1
+
+test_short_sha(){
+  given="${1}"
+  expected="${2}"
+
+  actual="$(short_sha ${given})"
+  echo "expected : [${expected}], actual : [${actual}]"
+  [ "${actual}" == "${expected}" ]
+}