Improve `hub merge` to not generate leftover remote refs

The previous implementation fetched refs into `refs/remotes/OWNER/BRANCH`.
Now, fetch `refs/pull/ID/head` directly into FETCH_HEAD and merge that.
It's a more straightforward approach that generates no artefacts.

This is for similarity with the reimplemented `hub checkout` command
which now also uses `refs/pull/ID/head`.

commands/merge.go

@@ -61,23 +61,30 @@ func transformMergeArgs(args *Args) error {
 		return err
 	}
 
+	repo, err := github.LocalRepo()
+	if err != nil {
+		return err
+	}
+
+	remote, err := repo.RemoteForRepo(pullRequest.Base.Repo)
+	if err != nil {
+		return err
+	}
+
 	branch := pullRequest.Head.Ref
 	headRepo := pullRequest.Head.Repo
 	if headRepo == nil {
 		return fmt.Errorf("Error: that fork is not available anymore")
 	}
 
-	u := url.GitURL(headRepo.Name, headRepo.Owner.Login, headRepo.Private)
-	mergeHead := fmt.Sprintf("%s/%s", headRepo.Owner.Login, branch)
-	ref := fmt.Sprintf("+refs/heads/%s:refs/remotes/%s", branch, mergeHead)
-	args.Before("git", "fetch", u, ref)
+	args.Before("git", "fetch", remote.Name, fmt.Sprintf("refs/pull/%s/head", id))
 
 	// Remove pull request URL
 	idx := args.IndexOfParam(mergeURL)
 	args.RemoveParam(idx)
 
-	mergeMsg := fmt.Sprintf("Merge pull request #%v from %s\n\n%s", id, mergeHead, pullRequest.Title)
-	args.AppendParams(mergeHead, "-m", mergeMsg)
+	mergeMsg := fmt.Sprintf("Merge pull request #%s from %s/%s\n\n%s", id, headRepo.Owner.Login, branch, pullRequest.Title)
+	args.AppendParams("FETCH_HEAD", "-m", mergeMsg)
 
 	if args.IndexOfParam("--ff-only") == -1 && args.IndexOfParam("--squash") == -1 && args.IndexOfParam("--ff") == -1 {
 		i := args.IndexOfParam("-m")

features/merge.feature

@@ -4,10 +4,21 @@ Feature: hub merge
     And the "origin" remote has url "git://github.com/defunkt/hub.git"
     And I am "mislav" on github.com with OAuth token "OTOKEN"
 
+  Scenario: Normal merge
+    When I run `hub merge master`
+    Then the git command should be unchanged
+
   Scenario: Merge pull request
     Given the GitHub API server:
       """
       get('/repos/defunkt/hub/pulls/164') { json \
+        :base => {
+          :repo => {
+            :owner => { :login => "defunkt" },
+            :name => "hub",
+            :private => false
+          }
+        },
         :head => {
           :ref => "hub_merge",
           :repo => {
@@ -19,10 +30,10 @@ Feature: hub merge
         :title => "Add `hub merge` command"
       }
       """
-    And there is a commit named "jfirebaugh/hub_merge"
+    And there is a git FETCH_HEAD
     When I successfully run `hub merge https://github.com/defunkt/hub/pull/164`
-    Then "git fetch git://github.com/jfirebaugh/hub.git +refs/heads/hub_merge:refs/remotes/jfirebaugh/hub_merge" should be run
-    And "git merge jfirebaugh/hub_merge --no-ff -m Merge pull request #164 from jfirebaugh/hub_merge" should be run
+    Then "git fetch origin refs/pull/164/head" should be run
+    And "git merge FETCH_HEAD --no-ff -m Merge pull request #164 from jfirebaugh/hub_merge" should be run
     When I successfully run `git show -s --format=%B`
     Then the output should contain:
       """
@@ -31,37 +42,18 @@ Feature: hub merge
       Add `hub merge` command
       """
 
-  Scenario: Merge pull request with --ff-only option
+  Scenario: Merge pull request with options
     Given the GitHub API server:
       """
       require 'json'
       get('/repos/defunkt/hub/pulls/164') { json \
-        :head => {
-          :ref => "hub_merge",
+        :base => {
           :repo => {
-            :owner => { :login => "jfirebaugh" },
+            :owner => { :login => "defunkt" },
             :name => "hub",
             :private => false
           }
         },
-        :title => "Add `hub merge` command"
-      }
-      """
-    And there is a commit named "jfirebaugh/hub_merge"
-    When I successfully run `hub merge --ff-only https://github.com/defunkt/hub/pull/164`
-    Then "git fetch git://github.com/jfirebaugh/hub.git +refs/heads/hub_merge:refs/remotes/jfirebaugh/hub_merge" should be run
-    And "git merge --ff-only jfirebaugh/hub_merge -m Merge pull request #164 from jfirebaugh/hub_merge" should be run
-    When I successfully run `git show -s --format=%B`
-    Then the output should contain:
-      """
-      Fast-forward (no commit created; -m option ignored)
-      """
-
-  Scenario: Merge pull request with --squash option
-    Given the GitHub API server:
-      """
-      require 'json'
-      get('/repos/defunkt/hub/pulls/164') { json \
         :head => {
           :ref => "hub_merge",
           :repo => {
@@ -73,99 +65,33 @@ Feature: hub merge
         :title => "Add `hub merge` command"
       }
       """
-    And there is a commit named "jfirebaugh/hub_merge"
-    When I successfully run `hub merge --squash https://github.com/defunkt/hub/pull/164`
-    Then "git fetch git://github.com/jfirebaugh/hub.git +refs/heads/hub_merge:refs/remotes/jfirebaugh/hub_merge" should be run
-    And "git merge --squash jfirebaugh/hub_merge -m Merge pull request #164 from jfirebaugh/hub_merge" should be run
-    When I successfully run `git show -s --format=%B`
-    Then the output should contain:
-      """
-      Fast-forward (no commit created; -m option ignored)
-      """
+    And there is a git FETCH_HEAD
+    When I successfully run `hub merge --squash https://github.com/defunkt/hub/pull/164 --no-edit`
+    Then "git fetch origin refs/pull/164/head" should be run
+    And "git merge --squash --no-edit FETCH_HEAD -m Merge pull request #164 from jfirebaugh/hub_merge" should be run
 
-  Scenario: Merge pull request with --ff option
+  Scenario: Merge pull request no repo
     Given the GitHub API server:
       """
       require 'json'
       get('/repos/defunkt/hub/pulls/164') { json \
-        :head => {
-          :ref => "hub_merge",
+        :base => {
           :repo => {
-            :owner => { :login => "jfirebaugh" },
+            :owner => { :login => "defunkt" },
             :name => "hub",
             :private => false
           }
         },
-        :title => "Add `hub merge` command"
-      }
-      """
-    And there is a commit named "jfirebaugh/hub_merge"
-    When I successfully run `hub merge --ff https://github.com/defunkt/hub/pull/164`
-    Then "git fetch git://github.com/jfirebaugh/hub.git +refs/heads/hub_merge:refs/remotes/jfirebaugh/hub_merge" should be run
-    And "git merge --ff jfirebaugh/hub_merge -m Merge pull request #164 from jfirebaugh/hub_merge" should be run
-    When I successfully run `git show -s --format=%B`
-    Then the output should contain:
-      """
-      Fast-forward (no commit created; -m option ignored)
-      """
-
-  Scenario: Merge private pull request
-    Given the GitHub API server:
-      """
-      require 'json'
-      get('/repos/defunkt/hub/pulls/164') { json \
         :head => {
           :ref => "hub_merge",
-          :repo => {
-            :owner => { :login => "jfirebaugh" },
-            :name => "hub",
-            :private => true
-          }
+          :repo => nil
         },
         :title => "Add `hub merge` command"
       }
       """
-    And there is a commit named "jfirebaugh/hub_merge"
-    When I successfully run `hub merge https://github.com/defunkt/hub/pull/164`
-    Then "git fetch git@github.com:jfirebaugh/hub.git +refs/heads/hub_merge:refs/remotes/jfirebaugh/hub_merge" should be run
-
-  Scenario: Missing repo
-    Given the GitHub API server:
-      """
-      require 'json'
-      get('/repos/defunkt/hub/pulls/164') { json \
-        :head => {
-          :ref => "hub_merge",
-          :repo => nil
-        }
-      }
-      """
     When I run `hub merge https://github.com/defunkt/hub/pull/164`
     Then the exit status should be 1
     And the stderr should contain exactly:
       """
       Error: that fork is not available anymore\n
       """
-
-  Scenario: Renamed repo
-    Given the GitHub API server:
-      """
-      require 'json'
-      get('/repos/defunkt/hub/pulls/164') { json \
-        :head => {
-          :ref => "hub_merge",
-          :repo => {
-            :owner => { :login => "jfirebaugh" },
-            :name => "hub-1",
-            :private => false
-          }
-        }
-      }
-      """
-    And there is a commit named "jfirebaugh/hub_merge"
-    When I successfully run `hub merge https://github.com/defunkt/hub/pull/164`
-    Then "git fetch git://github.com/jfirebaugh/hub-1.git +refs/heads/hub_merge:refs/remotes/jfirebaugh/hub_merge" should be run
-
-  Scenario: Unchanged merge
-    When I run `hub merge master`
-    Then "git merge master" should be run

features/steps.rb

@@ -82,6 +82,17 @@ Given(/^there is a commit named "([^"]+)"$/) do |name|
   run_silent %(git reset --quiet --hard HEAD^)
 end
 
+Given(/^there is a git FETCH_HEAD$/) do
+  empty_commit
+  empty_commit
+  in_current_dir do
+    File.open(".git/FETCH_HEAD", "w") do |fetch_head|
+      fetch_head.puts "%s\t\t'refs/heads/made-up' of git://github.com/made/up.git" % `git rev-parse HEAD`.chomp
+    end
+  end
+  run_silent %(git reset --quiet --hard HEAD^)
+end
+
 When(/^I make (a|\d+) commits?(?: with message "([^"]+)")?$/) do |num, msg|
   num = num == 'a' ? 1 : num.to_i
   num.times { empty_commit(msg) }