Emacs: Limiting Magit status to a directory

I’m probably using Git the wrong way. In addition to the nice neat repositories I have for various projects, I also sometimes have a big grab-bag repository that has random stuff in it, just so that I can locally version-control individual files without fussing about with Emacs’ numbered version systems. Sometimes I even remember to organize those files into directories.

When you have a Git repository that’s not one logical project but many little prototypes, using Magit status to work across the entire project can sometimes mean running into lots of distracting work in progress. I wanted a way to limit the scope of Magit status to a specific directory.

Here’s the experimental code I came up with:

      (defvar sacha/magit-limit-to-directory nil "Limit magit status to a specific directory.")
      (defun sacha/magit-status-in-directory (directory)
        "Displays magit status limited to DIRECTORY.
Uses the current `default-directory', or prompts for a directory
if called with a prefix argument. Sets `sacha/magit-limit-to-directory'
so that it's still active even after you stage a change. Very experimental."
        (interactive (list (expand-file-name
                            (if current-prefix-arg
                                (read-directory-name "Directory: ")
        (setq sacha/magit-limit-to-directory directory)
        (magit-status directory))

      (defadvice magit-insert-untracked-files (around sacha activate)
        (if sacha/magit-limit-to-directory
            (magit-with-section (section untracked 'untracked "Untracked files:" t)
              (let ((files (cl-mapcan
                            (lambda (f)
                              (when (eq (aref f 0) ??) (list f)))
                             "status" "--porcelain" "--" sacha/magit-limit-to-directory))))
                (if (not files)
                    (setq section nil)
                  (dolist (file files)
                    (setq file (magit-decode-git-path (substring file 3)))
                    (magit-with-section (section file file)
                      (insert "\t" file "\n")))
                  (insert "\n"))))

      (defadvice magit-insert-unstaged-changes (around sacha activate)
        (if sacha/magit-limit-to-directory
            (let ((magit-current-diff-range (cons 'index 'working))
                  (magit-diff-options (copy-sequence magit-diff-options)))
              (magit-git-insert-section (unstaged "Unstaged changes:")
                "--" sacha/magit-limit-to-directory

      (defadvice magit-insert-staged-changes (around sacha activate)
        "Limit to `sacha/magit-limit-to-directory' if specified."
        (if sacha/magit-limit-to-directory
            (let ((no-commit (not (magit-git-success "log" "-1" "HEAD"))))
              (when (or no-commit (magit-anything-staged-p))
                (let ((magit-current-diff-range (cons "HEAD" 'index))
                      (base (if no-commit
                                (magit-git-string "mktree")
                      (magit-diff-options (append '("--cached") magit-diff-options)))
                  (magit-git-insert-section (staged "Staged changes:")
                      (apply-partially #'magit-wash-raw-diffs t)
                    "diff-index" "--cached" base "--" sacha/magit-limit-to-directory))))

Now I can bind C-x v C-d to sacha/magit-status-in-directory and get something that lets me focus on one directory tree at a time. You can see my config in context at http://sachachua.com/dotemacs#magit

It feels like I’m probably trying to do things the Wrong Way and I should probably just break things out into separate repositories. Even though I realized this early on, though, I ended up digging into how to implement it just for the sheer heck of seeing if Emacs would let me do it. =) I don’t know how often I’ll use this function, but it was a good excuse to learn more about the way Magit works.

It took me an hour to find my way around magit.el, but that’s more my fault than the code’s. At first I tried to override magit-diff-options, but I eventually remembered that the paths need to come at the end of the command line arguments. (I had a cold! My brain was fuzzy!) It was fun poking around, though. Looking forward to learning even more about Magit!

  • jcs

    If you have a lot of single file repositories, you might want to look at Eric Raymond’s new SRC project.