Don't prompt before each invocation of the merge tool

Run merge conflict resolution tools to resolve merge conflicts.
More information: <https://git-scm.com/docs/git-mergetool>.
Trick copyright: tl;dr; <https://github.com/tldr-pages/tldr>

git mergetool --no-prompt

click the source code to copy install git mergetool on any operating system with command-not-found.com