Add Check How A File Is Being Ignored as a Git TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1468 TILs and counting..._
+_1469 TILs and counting..._
 
 ---
 
@@ -276,6 +276,7 @@ _1468 TILs and counting..._
 - [Auto-Squash Those Fixup Commits](git/auto-squash-those-fixup-commits.md)
 - [Caching Credentials](git/caching-credentials.md)
 - [Change The Start Point Of A Branch](git/change-the-start-point-of-a-branch.md)
+- [Check How A File Is Being Ignored](git/check-how-a-file-is-being-ignored.md)
 - [Checking Commit Ancestry](git/checking-commit-ancestry.md)
 - [Checkout Old Version Of A File](git/checkout-old-version-of-a-file.md)
 - [Checkout Previous Branch](git/checkout-previous-branch.md)

git/check-how-a-file-is-being-ignored.md

@@ -0,0 +1,28 @@
+# Check How A File Is Being Ignored
+
+There are a few places on your machine where you can specify the files that git
+should ignore. The most common is a repository's `.gitignore` file. The other
+places those excludes are specified can be more obscure. Fortunately, `git
+check-ignore` is a command that can show you specifically where.
+
+For instance, let's check why my `notes.md` file is being ignored.
+
+```bash
+$ git check-ignore -v .DS_Store
+.git/info/exclude:7:notes.md   notes.md
+```
+
+At some point I added it to my repo's `.git/info/exclude` file. The `-v` flag
+(_verbose_) when included with `check-ignore` tells me the file location.
+
+How about these pesky `.DS_Store` directories? How are those being ignored?
+
+```bash
+git check-ignore .DS_Store -v
+/Users/jbranchaud/.gitignore:3:.DS_Store        .DS_Store
+```
+
+Ah yes, I had added it to my _global exclude file_ which I've configured in
+`~/.gitconfig` to be the `~/.gitignore` file.
+
+See `man git-check-ignore` for more details.