Feature: Allow for customization of commit template

[steveluscher]

1. Since Sapling is most commonly used with GitHub, the commit template should use GitHub flavored markdown by default.

   <Replace this line with a title. Use 1 line only, 67 chars or less>
   
   ## Summary
   
   ## Test Plan
   

2. Beyond that, my request is for a way to customize the commit template, per repository.

[steveluscher]

cc/ @discentem, @quark-zju, @vegerot, who are working toward this in #524.

[quark-zju]

#524 is about the PR body template, not commit template. The commit template is already customizable via configuration (but PR template is not). You might want to change this line and surrounding configs to change the default template.

[steveluscher]

Awesome! Is that documented anywhere? I looked and looked for it in the docs and couldn’t find anything.