How do you achieve a numeric versioning scheme with Git?

Question

My organization is considering moving from SVN to Git. One argument against moving is as follows:

How do we do versioning?

We have an SDK distribution based on the NetBeans Platform. As the svn revisions are simple numbers we can use them to extend the version numbers of our plugins and SDK builds. How do we handle this when we move to Git?

Possible solutions:

• Using the build number from hudson (Problem: you have to check hudson to correlate that to an actual git version)
• Manually upping the version for nightly and stable (Problem: Learning curve, human error)

If someone else has encountered a similar problem and solved it, we'd love to hear how.

Answer 1

Use tags to mark commits with version numbers:

git tag -a v2.5 -m 'Version 2.5'

Push tags upstream—this is not done by default:

git push --tags

Then use the describe command:

git describe --tags --long

This gives you a string of the format:

v2.5-0-deadbeef
^    ^ ^
|    | |
|    | SHA of HEAD
|    |
|    number of commits since last tag
|
last tag

Answer 2

Versions are identified hashing the SHA1 hashes of all the files in the stored directory tree at the time of checkin. This hash is stored alongside the hashes of the parent checkin(s) so that the full history can be read.

Take a look at the process of using 'git-describe' by way of GIT-VERSION-GEN and how you can add this via your build process when you tag your release.

Here is a nice blog that gives an example of how to get what you want:

http://cd34.com/blog/programming/using-git-to-generate-an-automatic-version-number/

Answer 3

This has come up on a few projects for me. The best solution I've had so far is to generate a version number like this:

x.y.<number of commits>.r<git-hash>

Typically, it's generated by our build system using a combination of some static file or tag to get the major revision numbers, "git rev-list HEAD | wc -l" (which was faster than using git log), and "git rev-parse HEAD". The reasoning was follows:

1. We needed the ability to have high-level versioning happen explicitly (i.e. x.y)
2. When parallel development was happening, we needed to NEVER generate the same version number.
3. We wanted to easily track down where a version came from.
4. When parallel lines were merged, we wanted the new version to resolve higher than either of the branches.

Number 2 is invisible to most people, but is really important, and really difficult with distributed source control. SVN helps with this by giving you a single revision number. It turns out that a commit count is as close as you can get, while magically solving #4 as well. In the presence of branches, this is still not unique, in which case we add the hash, which neatly solves #3 as well.

Most of this was to accommodate deploying via Python's pip. This guaranteed that "pip install" would maybe be a bit odd during parallel development (i.e. packages from people on different branches would intermingle, but in a deterministic fashion), but that after merges, everything sorted out. Barring the presence of an exposed rebase or amend, this worked quite nicely for the above requirements.

In case you're wondering, we chose to put the r in front of the hash due to some weirdness with how Python packaging handles letters in version numbers (i.e. a-e are less than 0, which would make "1.3.10.a1234" < "1.3.10" < "1.3.10.1234").

Answer 4

This might be a bit overkill, but I'll let you know how we do it.

We use a branching structure very similar to this.

Hudson builds off our "develop" branches and increments build numbers starting from 0. The build number is unique to each project and gets tagged in version control. The reason is so that you can tell exactly which develop branch build 42 came from, for example (each project can have several develop branches in parallel, because each project can have several teams working on different aspects of the project).

When we decide that a particular build is good enough to be released, the commit that triggered that build gets tagged with a release version number, which is decided by marketing. This means that the dev teams don't care about what the final version number is and marketing is free to shuffle around version numbers as it sees fit. The final version number and build number are both present in the released product.

Example: 2.1.0 build 1337

This means, for a specific product release, you can tell which was the last team to have worked on it and you can query git for all the commits leading up to release to diagnose a problem if you need to.

Answer 5

Pro Git in section 7.2 "Git Attributes" in "Keyword" Expansion part contains a nice example of using smudge&clean filters for generating RCS-style keywords. You can use the same technique for embedding some-version-string into code, formatted and calculated according to your rules. You still can use git describe as a staring point, but you have the possibility to transform to any more appropriate form and get from v2.5-14-feebdaed, for example, clean 2.5.14