.gitconfig: Add comments

.gitconfig

@@ -1,15 +1,26 @@
 [alias]
-	l = log -p
-	s = status
+	# View the SHA, description, and history graph of the latest 20 commits
+	l = log --pretty=oneline -n 20 --graph
+	# View the current working tree status using the short format
+	s = status -s
+	# Pull in remote changes for the current repository and all its submodules
 	p = !"git pull; git submodule foreach git pull origin master"
+	# Undo a `git push`
 	undopush = push -f origin HEAD^:master
+
 [apply]
+	# Detect whitespace errors when applying a patch
 	whitespace = fix
+
 [core]
+	# Use custom `.gitignore` and `.gitattributes`
 	excludesfile = ~/.gitignore
 	attributesfile = ~/.gitattributes
-	whitespace = fix,space-before-tab,tab-in-indent,trailing-space
+	# Treat spaces before tabs, lines that are indented with 8 or more spaces, and all kinds of trailing whitespace as an error
+	whitespace = space-before-tab,indent-with-non-tab,trailing-space
+
 [color]
+	# Use colors in Git commands that are capable of colored output when outputting to the terminal
 	ui = auto
 [color "branch"]
 	current = yellow reverse
@@ -25,7 +36,10 @@
 	changed = green
 	untracked = cyan
 [merge]
+	# Include summaries of merged commits in newly created merge commit messages
 	log = true
+
+# URL shorthands
 [url "git@github.com:"]
 	insteadOf = "gh:"
 	pushInsteadOf = "github:"