Delete merged and squashed from other branches. (#11)

This defaults to master currently, my change proposes that the script should take an argument and allow squashed branches to be pruned no matter where they were merged.

README.md

@@ -11,16 +11,24 @@ This is useful if you work on a project that squashes branches into master. Afte
 To run as a shellscript, simply copy the following command (setting up an alias is recommended). There's no need to clone the repo.
 
 ```bash
-git checkout -q master && git for-each-ref refs/heads/ "--format=%(refname:short)" | while read branch; do mergeBase=$(git merge-base master $branch) && [[ $(git cherry master $(git commit-tree $(git rev-parse $branch\^{tree}) -p $mergeBase -m _)) == "-"* ]] && git branch -D $branch; done
+# Change $TARGET_BRANCH to your targeted branch, e.g. change from `master` to `main` to delete branches squashed into `main`.
+TARGET_BRANCH=master && git checkout -q $TARGET_BRANCH && git for-each-ref refs/heads/ "--format=%(refname:short)" | while read branch; do mergeBase=$(git merge-base $TARGET_BRANCH $branch) && [[ $(git cherry $TARGET_BRANCH $(git commit-tree $(git rev-parse $branch\^{tree}) -p $mergeBase -m _)) == "-"* ]] && git branch -D $branch; done
+# OR you can put this function in a global git alias and call it like this
+# `git delete-squashed` OR `git delete-squashed main`
+git config --global alias.delete-squashed '!f() { local targetBranch=${1:-master} && git checkout -q $targetBranch && git branch --merged | grep -v "\*" | xargs -n 1 git branch -d && git for-each-ref refs/heads/ "--format=%(refname:short)" | while read branch; do mergeBase=$(git merge-base $targetBranch $branch) && [[ $(git cherry $targetBranch $(git commit-tree $(git rev-parse $branch^{tree}) -p $mergeBase -m _)) == "-"* ]] && git branch -D $branch; done; }; f'
 ```
 
 ### Node.js
 
 You can also install the tool as a Node.js package from NPM. (The package code is in this repo.)
 
+Additionally, you can specify an alternate branch to check for squashed merges, as well. This is useful for different names of trunk branches like `main` or `develop`.
+
 ```bash
 $ npm install --global git-delete-squashed
 $ git-delete-squashed
+$ # Specify a different branch name like so
+$ git-delete-squashed main
 ```
 
 ## Details

bin/git-delete-squashed.js

@@ -5,6 +5,8 @@
 const childProcess = require('child_process');
 const Promise = require('bluebird');
 const DEFAULT_BRANCH_NAME = 'master';
+const RUN_WITH_NODE = process.argv[0].includes('node');
+const selectedBranchName = process.argv[RUN_WITH_NODE ? 2 : 1] || DEFAULT_BRANCH_NAME;
 
 /**
  * Calls `git` with the given arguments from the CWD
@@ -28,20 +30,20 @@ function git (args) {
 git(['for-each-ref', 'refs/heads/', '--format=%(refname:short)'])
   .then(branchListOutput => branchListOutput.split('\n'))
   .tap(branchNames => {
-    if (branchNames.indexOf(DEFAULT_BRANCH_NAME) === -1) {
-      throw `fatal: no branch named '${DEFAULT_BRANCH_NAME}' found in this repo`;
+    if (branchNames.indexOf(selectedBranchName) === -1) {
+      throw `fatal: no branch named '${selectedBranchName}' found in this repo`;
     }
   }).filter(branchName =>
     // Get the common ancestor with the branch and master
     Promise.join(
-      git(['merge-base', DEFAULT_BRANCH_NAME, branchName]),
+      git(['merge-base', selectedBranchName, branchName]),
       git(['rev-parse', `${branchName}^{tree}`]),
       (ancestorHash, treeId) => git(['commit-tree', treeId, '-p', ancestorHash, '-m', `Temp commit for ${branchName}`])
     )
-      .then(danglingCommitId => git(['cherry', DEFAULT_BRANCH_NAME, danglingCommitId]))
+      .then(danglingCommitId => git(['cherry', selectedBranchName, danglingCommitId]))
       .then(output => output.startsWith('-'))
   )
-  .tap(branchNamesToDelete => branchNamesToDelete.length && git(['checkout', DEFAULT_BRANCH_NAME]))
+  .tap(branchNamesToDelete => branchNamesToDelete.length && git(['checkout', selectedBranchName]))
   .mapSeries(branchName => git(['branch', '-D', branchName]))
   .mapSeries(stdout => console.log(stdout))
   .catch(err => console.error(err.cause || err));