feat: command to simulate Merge/Pull Request

- Adds `git merge(M|P)R <source_branch> <target_branch> [--delete-after-merge]` command
to simulate a Merge/Pull Request being merged into the target branch
- The optional flag `--delete-after-merge` will remove the merged branch on the origin tree
  - The local remote branch remains as it is Git default behavior, even after `git fetch`
(it would require `git fetch --prune` support to automatically prune remote tracking branches)
- You can push a branch with a deleted remote tracking branch on origin, the ref will just update.

Resolves #1057

__tests__/remote.spec.js

@@ -1,5 +1,8 @@
 var base = require('./base');
+var intl = require('../src/js/intl');
+var Q = require('q');
 var expectTreeAsync = base.expectTreeAsync;
+var runCommand = base.runCommand;
 
 describe('Git Remotes', function() {
   it('clones', function() {
@@ -242,6 +245,20 @@ describe('Git Remotes', function() {
     );
   });
 
+  it('will push to a new remote branch if tracking was previously set up but remote branch was merged on origin', function() {
+    return expectTreeAsync(
+      `git clone;
+      git switch -c feat;
+      git commit;
+      git push;
+      git fakeTeamwork;
+      git mergeMR feat main --delete-after-merge;
+      git commit;
+      git push;`,
+      '{"branches":{"main":{"remoteTrackingBranchID":"o/main","target":"C1","id":"main"},"o/main":{"remoteTrackingBranchID":null,"target":"C1","id":"o/main"},"feat":{"remoteTrackingBranchID":"o/feat","target":"C5","id":"feat"},"o/feat":{"remoteTrackingBranchID":null,"target":"C5","id":"o/feat"}},"commits":{"C0":{"parents":[],"id":"C0","rootCommit":true},"C1":{"parents":["C0"],"id":"C1"},"C2":{"parents":["C1"],"id":"C2"},"C5":{"parents":["C2"],"id":"C5"}},"tags":{},"HEAD":{"id":"HEAD","target":"feat"},"originTree":{"branches":{"main":{"remoteTrackingBranchID":null,"target":"C4","id":"main"},"feat":{"remoteTrackingBranchID":null,"target":"C5","id":"feat"}},"commits":{"C0":{"parents":[],"id":"C0","rootCommit":true},"C1":{"parents":["C0"],"id":"C1"},"C2":{"parents":["C1"],"id":"C2"},"C3":{"parents":["C1"],"id":"C3"},"C4":{"parents":["C3","C2"],"id":"C4"},"C5":{"parents":["C2"],"id":"C5"}},"tags":{},"HEAD":{"target":"main","id":"HEAD"}}}'
+    );
+  });
+
   it('will not fetch if ref does not exist on remote', function() {
     return expectTreeAsync(
       'git clone; git fakeTeamwork; git fetch foo:main',
@@ -440,5 +457,64 @@ describe('Git Remotes', function() {
     );
   });
 
+  describe('mergeMR/mergePR on remote', function() {
+    it('requires a remote', function() {
+      return runCommand('git mergeMR', function(commandMsg) {
+        expect(commandMsg).toBe(intl.str('git-error-origin-required'));
+      });
+    });
 
+    it('requires exactly 2 parameters', function() {
+      return Q.all([
+        runCommand('git clone; git mergeMR', function(commandMsg) {
+          expect(commandMsg).toBe(
+            intl.str('git-error-args-few', {
+              lower: '2',
+              what: 'with git mergeMR',
+            })
+          );
+        }),
+        runCommand('git clone; git mergeMR feat', function(commandMsg) {
+          expect(commandMsg).toBe(
+            intl.str('git-error-args-few', {
+              lower: '2',
+              what: 'with git mergeMR',
+            })
+          );
+        }),
+        runCommand('git clone; git mergeMR a b main', function(commandMsg) {
+          expect(commandMsg).toBe(
+            intl.str('git-error-args-many', {
+              upper: '2',
+              what: 'with git mergeMR',
+            })
+          );
+        }),
+      ]);
+    });
+
+    it('merges one remote branch into another', function() {
+      return expectTreeAsync(
+        `git clone;
+        git switch -c feat;
+        git commit;
+        git push;
+        git fakeTeamwork;
+        git mergeMR feat main`,
+        '{"branches":{"main":{"target":"C1","id":"main","remoteTrackingBranchID":"o/main"},"o/main":{"target":"C1","id":"o/main","remoteTrackingBranchID":null},"feat":{"target":"C2","id":"feat","remoteTrackingBranchID":"o/feat"},"o/feat":{"target":"C2","id":"o/feat","remoteTrackingBranchID":null}},"commits":{"C0":{"parents":[],"id":"C0","rootCommit":true},"C1":{"parents":["C0"],"id":"C1"},"C2":{"parents":["C1"],"id":"C2"}},"tags":{},"HEAD":{"target":"feat","id":"HEAD"},"originTree":{"branches":{"main":{"target":"C4","id":"main","remoteTrackingBranchID":null},"feat":{"target":"C2","id":"feat","remoteTrackingBranchID":null}},"commits":{"C0":{"parents":[],"id":"C0","rootCommit":true},"C1":{"parents":["C0"],"id":"C1"},"C2":{"parents":["C1"],"id":"C2"},"C3":{"parents":["C1"],"id":"C3"},"C4":{"parents":["C3","C2"],"id":"C4"}},"tags":{},"HEAD":{"target":"main","id":"HEAD"}}}'
+      );
+    });
+
+    it('deletes the merged remote branch after merging', function() {
+      return expectTreeAsync(
+        `git clone;
+        git switch -c feat;
+        git commit;
+        git push;
+        git fakeTeamwork;
+        git mergeMR feat main --delete-after-merge`,
+        '{"branches":{"main":{"target":"C1","id":"main","remoteTrackingBranchID":"o/main"},"o/main":{"target":"C1","id":"o/main","remoteTrackingBranchID":null},"feat":{"target":"C2","id":"feat","remoteTrackingBranchID":"o/feat"},"o/feat":{"target":"C2","id":"o/feat","remoteTrackingBranchID":null}},"commits":{"C0":{"parents":[],"id":"C0","rootCommit":true},"C1":{"parents":["C0"],"id":"C1"},"C2":{"parents":["C1"],"id":"C2"}},"tags":{},"HEAD":{"target":"feat","id":"HEAD"},"originTree":{"branches":{"main":{"target":"C4","id":"main","remoteTrackingBranchID":null}},"commits":{"C0":{"parents":[],"id":"C0","rootCommit":true},"C1":{"parents":["C0"],"id":"C1"},"C2":{"parents":["C1"],"id":"C2"},"C3":{"parents":["C1"],"id":"C3"},"C4":{"parents":["C3","C2"],"id":"C4"}},"tags":{},"HEAD":{"target":"main","id":"HEAD"}}}'
+      );
+    });
+  });
 });

src/js/git/commands.js

@@ -589,6 +589,47 @@ var commandConfig = {
     }
   },
 
+  mergeMR: {
+    regex: /^git +merge[MP]R($|\s)/,
+    options: ['--delete-after-merge'],
+    execute: function(engine, command) {
+      var generalArgs = command.getGeneralArgs();
+      var commandOptions = command.getOptionsMap();
+      if (!engine.hasOrigin()) {
+        throw new GitError({
+          msg: intl.str('git-error-origin-required'),
+        });
+      }
+
+      command.validateArgBounds(generalArgs, 2, 2);
+
+      var fromBranch = validateOriginBranchName(engine, generalArgs[0]);
+      var intoBranch = validateOriginBranchName(engine, generalArgs[1]);
+
+      var origin = engine.origin;
+
+      origin.checkout(intoBranch);
+      var mergeCommit = origin.merge(fromBranch, { noFF: true });
+
+      origin.animationFactory.genCommitBirthAnimation(
+        origin.animationQueue,
+        mergeCommit,
+        origin.gitVisuals
+      );
+
+      if (!!commandOptions['--delete-after-merge']) {
+        origin.validateAndDeleteBranch(fromBranch);
+      }
+
+      origin.checkout('main');
+
+      origin.animationFactory.playRefreshAnimationAndFinish(
+        origin.gitVisuals,
+        origin.animationQueue
+      );
+    }
+  },
+
   revlist: {
     dontCountForGolf: true,
     displayName: 'rev-list',

src/js/git/index.js

@@ -453,10 +453,17 @@ GitEngine.prototype.findCommonAncestorWithRemote = function(originTarget) {
 };
 
 GitEngine.prototype.makeBranchOnOriginAndTrack = function(branchName, target) {
-  var remoteBranch = this.makeBranch(
+  var remoteBranch = this.refs[ORIGIN_PREFIX + branchName];
+
+  // If the remote branch exists but the branch on origin was deleted, updates its target location
+  if (remoteBranch) {
+    this.setTargetLocation(remoteBranch, target);
+  } else {
+    remoteBranch = this.makeBranch(
       ORIGIN_PREFIX + branchName,
       this.getCommitFromRef(target)
     );
+  }
 
   if (this.refs[branchName]) { // not all remote branches have tracking ones
     this.setLocalToTrackRemote(this.refs[branchName], remoteBranch);