Separate checkout strategies more cleanly (#135)

* Separated checkout strategies to separate independent implementations, using the checkoutStrategy interface.

* If commit, branch and tag is specified, no longer adding branch ref to the fetch command. This is the same behavior as checking out commit+branch, the fetch is not branch specific.

* Created Exported parameters to serve as a public API (for describe the required input parameters for all checkout methods). (To be used in the webhook handler)

* Submodule update is moved after checkout, as it is independent from other checkout actions (after detaching head).

bitrise.yml

@@ -59,6 +59,7 @@ workflows:
     - _test_hosted_git_notfork
     - _test_unrelated_histories
     - _test_hosted_git_ssh_prefix
+    - test_diff_file
 
   _test_submodule:
     before_run:
@@ -576,6 +577,70 @@ workflows:
         inputs:
         - dir_to_check: $CLONE_INTO_DIR
 
+  test_diff_file:
+    before_run:
+    - _create_tmpdir
+    steps:
+    - script:
+        inputs:
+        - content: |-
+            #!/bin/env bash
+            set -ex
+            DIFF_DIR=$(pwd)/diff_dir
+            GIT_DIR=$(pwd)/repoA
+            PR_GIT_DIR=$(pwd)/repoB
+            CLONE_DIR=$(pwd)/cloneDir
+            mkdir ${GIT_DIR}
+            mkdir ${PR_GIT_DIR}
+            mkdir ${DIFF_DIR}
+            mkdir ${CLONE_DIR}
+
+            # Repo A
+            cd ${GIT_DIR}
+            git init
+            echo "aabbccdd" > README.md
+            git add .
+            git commit -m "Initial commit A"
+            cd -
+
+            # Repo B (clone of Repo A)
+            cd ${PR_GIT_DIR}
+            git clone ${GIT_DIR} .
+            echo "eeffgghh" >>README.md
+            git add .
+            git commit -m "PR commit B"
+            
+            # Diff files
+            git diff HEAD^ HEAD | tee -a ${DIFF_DIR}/diff.txt
+            cd -
+            
+            # Set envs
+            envman add --key CLONE_INTO_DIR --value ${CLONE_DIR}
+            envman add --key GIT_REPOSITORY_URL --value ${GIT_DIR}
+            envman add --key PR_REPOSITORY_URL --value ${PR_GIT_DIR}
+            envman add --key BITRISE_BUILD_URL --value "file://${DIFF_DIR}"
+    - path::./:
+        run_if: true
+        inputs:
+        - repository_url: $GIT_REPOSITORY_URL
+        - clone_into_dir: $CLONE_INTO_DIR
+        - pull_request_id: 8
+        - pull_request_repository_url: $PR_REPOSITORY_URL
+        - pull_request_merge_branch: ""
+        - branch_dest: "master"
+        - branch: "master"
+        - commit: ""
+        - tag: ""
+        - clone_depth: "1"
+        - manual_merge: "no"
+    - script:
+        inputs:
+        - content: |-
+            #!/bin/bash
+            set -ex
+            eval "$EVAL_SCRIPT"
+            diff ${CLONE_INTO_DIR}/README.md ${PR_REPOSITORY_URL}/README.md
+
   _test_too_long_commit_message:
     before_run:
       - _create_tmpdir
@@ -621,23 +686,6 @@ workflows:
         inputs:
         - path: $STEP_TMPDIR
 
-  # ----------------------------------------------------------------
-  # --- Utility workflows
-  dep-update:
-    title: Dep update
-    description: |
-      Used for updating bitrise dependencies with dep
-    steps:
-    - script:
-        title: Dependency update
-        inputs:
-        - content: |-
-            #!/bin/bash
-            set -ex
-            go get -u -v github.com/golang/dep/cmd/dep
-            dep ensure -v
-            dep ensure -v -update
-
   # ----------------------------------------------------------------
   # --- workflow to Share this step into a Step Library
   audit-this-step: