[PATCH v2] .github/PULL_REQUEST_TEMPLATE.md: add a note about single-commit PRs

From: Philippe Blain <levraiphilippeblain@gmail.com>

Contributors using Gitgitgadget continue to send single-commit PRs with their commit message text duplicated below the three-dash line, increasing the signal-to-noise ratio for reviewers.

This is because Gitgitgadget copies the pull request description as an in-patch commentary, for single-commit PRs, and _GitHub_ defaults to prefilling the pull request description with the commit message, for single-commit PRs (followed by the content of the pull request template).

Add a note in the pull request template mentioning that for single-commit PRs, the PR description should thus be kept empty, in the hope that contributors read it and act on it.

This partly addresses: https://github.com/gitgitgadget/gitgitgadget/issues/340

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
---
    .github/PULL_REQUEST_TEMPLATE.md: add a note about single-commit PRs
    
    Changes since v1:
    
     * simplified the wording as suggested by Junio

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1665%2Fphil-blain%2Fempty-description-single-commit-prs-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1665/phil-blain/empty-description-single-commit-prs-v2
Pull-Request: https://github.com/git/git/pull/1665

Range-diff vs v1:

 1:  4786f84884a ! 1:  f719e11b1df .github/PULL_REQUEST_TEMPLATE.md: add a note about single-commit PRs
     @@ .github/PULL_REQUEST_TEMPLATE.md: a mailing list (git@vger.kernel.org) for code
       bug reports. Nevertheless, you can use GitGitGadget (https://gitgitgadget.github.io/)
       to conveniently send your Pull Requests commits to our mailing list.
       
     -+If you use Gitgitgadget for a single-commit pull request, please *leave the pull
     -+request description empty*: your commit message itself should describe your
     -+changes.
     ++For a single-commit pull request, please *leave the pull request description
     ++empty*: your commit message itself should describe your changes.
      +
       Please read the "guidelines for contributing" linked above!

 .github/PULL_REQUEST_TEMPLATE.md | 3 +++
 1 file changed, 3 insertions(+)