September 4, 2011

Since I have a tag dedicated to version control, I thought to use it to link to iolaus, a git porcelain that emulates darcs. It’s written by the same guy who wrote darcs, possibly as a one-off project. Perhaps it was meant to solve the darcs "exponential merge time" problem. The same problem has been drastically improved in Darcs 2, and iolaus hasn’t been updated since March 2010, so it probably isn’t worth worrying a lot about.

I realized that the semantics of git are actually not nearly so far from those of darcs as I had previously thought. In particular, if we view each commit as describing a patch in its "primitive context" (to use darcs-speak), then there is basically a one-to-one mapping from darcs’ semantics to a git repository. The catch is that it must be a git repository with multiple heads!

Fortunately, this is not such a foreign concept to git. In fact, git has a whole framework to help users manage repositories with multiple heads (see, e.g. checkout and branch). So it’s not so very foreign at all. There are just a couple of major differences how git works. First, in git your working directory will only reflect one of the heads, while in darcs (or iolaus) the working directory reflects the union of all changes in the repository.

Just to make things even more interesting, it’s written in Go.

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Emacs Got Git

April 29, 2010

I saw Emacs Got Git, sometimes called "Egg", listed on the list of git-related software on the git wiki (although now taken down) and of course on the EmacsWiki. I decided I’d give it a whirl. The most recent version I could find was the one listed on the EmacsWiki, the version from bplayer, which seems to still be actively developed. The incumbent here is either magit, which is by far the best user interface I’ve ever seen for any version control anywhere, or VC mode, which was written once to support SCCS and has largely survived unchanged since then.

A brief digression about magit and vc-mode. Magit is a little bit of a challenge to pick up: you actually have to read the manual. But the short version is: M-x magit-status to open a view of your repository, and then TAB things open and closed. You can press "s" to stage files, hunks, or even "highlight" lines using the region and stage only those. "u" to unstage; "c" to start a commit, and then C-c C-c to make the commit. You can create a commit that amends the previous commit by pressing C-c C-a in the log message buffer. It probably offends some that there are already conventions here for VC system integration, notably vc-mode. But vc-mode takes a file-based view of version control, has no support for staging hunks, and in general just doesn’t feel good to use. magit is much better — so much better that it is easily worth the break in convention.

So I thought I’d check out Emacs Got Git, to see if it was any better than magit. This isn’t a detailed analysis — actually I’ve probably spent longer writing this post than I did looking at Egg.

I find a screenshot is worth a thousand words. On my ~/etc repository, magit looks like this:


Magit highlights all the important details: which files are changed? Which are untracked? What commits exist locally that don’t exist on the remote?

On the same repo, Egg looks like this:


This is what we call the "angry fruit salad" school of UI design. Also, it doesn’t have a section for "unpushed" commits.

I’m going to be sticking with magit for the forseeable future.

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Fossil: new DVCS

October 30, 2009

Those of you who care about version control should be aware of Fossil. Distributed version control, like NoSQL databases, has rapidly sprouted a ton of contenders like mushrooms, and I’m not especially convinced of this one’s superiority to the incumbents (i.e. git, bzr, or darcs).

In addition to doing distributed version control like Git and Mercurial, Fossil also supports distributed bug tracking and distributed wiki all in a single integrated package… Fossil has a built-in and easy-to-use web interface that simplifies project tracking and promotes situational awareness. Simply type "fossil ui" from within any check-out and Fossil automatically opens your web browser in a page that gives detailed history and status information on that project.

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