2718.us blog » mercurial

Integrating Version Control Revisions in Mac App Version Numbers

2718.us — Mon, 22 Mar 2010 13:57:26 +0000

When I was using Subversion for version control in working on my Mac apps in Xcode, I had come to use a build script phase to tack on the subversion revision number as the last part to the version number:

# tack the subversion revision number onto the CFBundleVersion

REV=`svnversion -n "${PROJECT_DIR}"`
REV=${REV/#[0-9]*:/}
REV=${REV//[^0-9]/}
BASE=`/usr/libexec/PlistBuddy -c "Print :CFBundleVersion" "${PROJECT_DIR}/Info.plist"`
/usr/libexec/PlistBuddy -c "Set :CFBundleVersion $BASE.$REV" "${TARGET_BUILD_DIR}/${INFOPLIST_PATH}"

This takes the CFBundleVersion from the project’s Info.plist, adds a period and the subversion revision number, and injects that into the Info.plist of the built product.

When I made the move to Mercurial, I couldn’t quite do this anymore. While subversion revision numbers are monotone increasing and consistent everywhere (they are the unique identifiers of a particular version), Mercurial’s “revision numbers” are local to a particular instance of the repository and may not match up from one instance to another. Mercurial uses a hash as the unique identifier of a particular version, and these hexadecimal hashes are not monotone, making them unsuitable for use in CFBundleVersion.

Though it took some time, I’ve finally come to a system with Mercurial that I think is workable:

# use the number of minutes between the tip and the most recent tagged commit

HG_LAST_TAG_TIMESTAMP=$(/usr/local/bin/hg log -r "$(/usr/local/bin/hg log -r '.' –template '{latesttag}' –repository "${PROJECT_DIR}|>")" –template "{date|hgdate}\n" –repository "${PROJECT_DIR}" | cut -f1 -d' ')
HG_TIP_TIMESTAMP=$(/usr/local/bin/hg log -r '.' –template "{date|hgdate}\n" –repository "${PROJECT_DIR}" | cut -f1 -d' ')
REV=$(( ($HG_TIP_TIMESTAMP – $HG_LAST_TAG_TIMESTAMP) / 60 ))
BASE=`/usr/libexec/PlistBuddy -c "Print :CFBundleVersion" "${PROJECT_DIR}/Info.plist"`
/usr/libexec/PlistBuddy -c "Set :CFBundleVersion $BASE.$REV" "${TARGET_BUILD_DIR}/${INFOPLIST_PATH}"

This calculates the number of minutes between the most recent tagged ancestor of the tip and the tip itself and adds that to the CFBundleVersion. Because it’s time-based, it is guaranteed to be monotone increasing, consistent, and unique (well, provided multiple commits don’t happen within a 1-minute span, which is safe for me).

Converting a Google Code Project from Subversion to Mercurial

2718.us — Sun, 21 Mar 2010 15:01:33 +0000

The Google Code support wiki article ConvertingSvnToHg is quite easy to follow, but there is one thing worth noting that is kind of buried in the comments. Assuming you’re doing full history conversion, it is very useful to know that running hg convert locally is much much faster than running it on a remote SVN repository, so it is well worth using svnsync to make a local mirror of the SVN repository and then run hg convert on that.

Subversions is (on its way) Out, Mercurial is In

2718.us — Sat, 20 Mar 2010 14:33:24 +0000

I have very happily been using Subversion since 2008. I was quite clearly late to the version control system (VCS) party and I wish I’d known about VCS much earlier. About 5-6 months ago, I finally gave in and tried Mercurial and hated it. While I could kind of get my head around why I should like a distributed VCS (DVCS), I just couldn’t make the paradigm work for me. I was pretty sure that with all the people talking about how great DVCS was, I must be doing something wrong, but that didn’t stop me from putting Mercurial back on the shelf.

A little over a month ago, I went back and played with Mercurial some more, and it just clicked. I think it had something to do with reading the Mercurial guide, but I couldn’t really put my finger on it. That is, until a few days ago, when I read Distributed Version Control is here to stay, baby. Joel’s explanation of his transition to DVCS really hit on the shift in thinking that took place for me in moving to Mercurial. Plus, it has one of the best lines I’ve ever read in a blog post:

If you are using Subversion, stop it. Just stop. Subversion = Leeches. Mercurial and Git = Antibiotics. We have better technology now.