Move pages under tldr, lint run.sh, update docs

tldr/git-difftool

@@ -0,0 +1,26 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# git difftool
+
+> Show file changes using external diff tools. Accepts the same options and arguments as `git diff`.
+> See also: `git diff`.
+> More information: <https://git-scm.com/docs/git-difftool>.
+
+- List available diff tools:
+
+`git difftool --tool-help`
+
+- Set the default diff tool to meld:
+
+`git config --global diff.tool "{{meld}}"`
+
+- Use the default diff tool to show staged changes:
+
+`git difftool --staged`
+
+- Use a specific tool (opendiff) to show changes since a given commit:
+
+`git difftool --tool={{opendiff}} {{commit}}`