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+# Integrating with Git: A Field Guide
+
+Pretty much everything you might want to do to a Git repository when writing
+tooling or integrations should be done by shelling out to one `git` command or
+another.
+
+## Finding Git's trees
+
+Git commands can be invoked from locations other than the root of the work
+tree or git directory. You can find either of those by invoking `git
+rev-parse`.
+
+To find the absolute path to the root of the work tree:
+
+    git rev-parse --show-toplevel
+
+This will output the absolute path to the root of the work tree on standard
+output, followed by a newline. Since the work tree's absolute path can contain
+whitespace (including newlines), you should assume every byte of output save
+the final newline is part of the path, and if you're using this in a shell
+script, quote defensively.
+
+To find the relative path from the current working directory:
+
+    git rev-parse --show-cdup
+
+This will output the relative path to the root of the work tree on standard
+output, followed by a newline.
+
+For bare repositories, both commands will output nothing and exit with a zero
+status. (Surprise!)
+
+To find *a* path to the root of the git directory:
+
+    git rev-parse --git-dir
+
+This will output either the relative or the absolute path to the git
+directory, followed by a newline.
+
+All three of these commands will exit with non-zero status when run outside of
+a work tree or git directory. Check for it.