Add Show Summary Stats For Current Branch as a Git TIL

git/show-summary-stats-for-current-branch.md

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+# Show Summary Stats For Current Branch
+
+When I push a branch up to GitHub as a PR, there is a part of the UI that shows
+you how many lines you've added and removed for this branch. It bases that off
+the target branch which is typically your `main` branch.
+
+The `git diff` command can provide those same stats right in the terminal. The
+key is to specify the `--shortstat` flag which tells `git` to exclude other diff
+output and only show:
+
+- Number of files changed
+- Number of insertions
+- Number of deletions
+
+Here is the summary stats for a branch I'm working on:
+
+```bash
+❯ git diff --shortstat main
+ 8 files changed, 773 insertions(+), 25 deletions(-)
+```
+
+We have to be on our feature branch and then we point to the branch (or whatever
+ref) we want to diff against. Since I want to know how my feature branch
+compares to `main`, I specify that.
+
+See `man git-diff` for more details.