feat: allow specifying nightly builds

The `version` field now accepts two additional fields:
- A sha1 git hash of a `main` commit
- The value `"head"` for the latest commit on `main`

Signed-off-by: Justin Chadwell <me@jedevc.com>

Author: jedevc

action.yml

@@ -47,17 +47,38 @@ runs:
         fi
         printf '%s/bin' "$prefix_dir" >> $GITHUB_PATH
 
-        # If the dagger version is 'latest', set the version back to an empty
-        # string. This allows the install script to detect and install the latest
-        # version itself
-        VERSION=${{ inputs.version }}
+        # Determine the version to install
         if [[ "$VERSION" == "latest" ]]; then
-          VERSION=
+          # Get the latest version.
+          #
+          # Set the version back to an empty string. This allows the install
+          # script to detect and install the latest version itself.
+          VERSION=""
+        elif [[ "$VERSION" =~ ^v ]]; then
+          # Get the specified version.
+          #
+          # No need to set anything.
+          :
+        elif [[ "$VERSION" == "head" ]]; then
+          # Get the latest nightly build from "main".
+          #
+          # Set the commit to "head".
+          COMMIT="$VERSION"
+          VERSION=""
+        elif [[ "$VERSION" =~ [a-z0-9]{40} ]]; then
+          # Get the specified nightly build from "main".
+          #
+          # Set the commit to the specified commit sha.
+          COMMIT="$VERSION"
+          VERSION=""
+        else
+          echo "Invalid version specified: $VERSION"
+          exit 1
         fi
 
         # The install.sh script creates path ${prefix_dir}/bin
         curl -fsS https://dl.dagger.io/dagger/install.sh \
-        | BIN_DIR=${prefix_dir}/bin DAGGER_VERSION=$VERSION sh
+        | BIN_DIR=${prefix_dir}/bin DAGGER_VERSION=$VERSION DAGGER_COMMIT=$COMMIT sh
 
     - shell: bash
       env: