git describe fails with "fatal: No names found, cannot describe anything."

Question

I'm using git 1.7.1 on Ubuntu 10.10 amd64, and I'm trying to extract the hash of my repository HEAD to use it in an automated version information that I compile into my project.

In the past, this always worked by using

git describe --tags 

however, git is now throwing

fatal: No names found, cannot describe anything. 

at me. Does anyone have a clue what that means?

Google showed only few hits and no solution.

Answer 1

If you want the id of your HEAD then you don't need describe, you should just use rev-parse.

git rev-parse HEAD 

If you want an abbreviated hash you can use --short.

git rev-parse --short HEAD 

If you want a "describe" to fall back to an abbreviated hash if it can't find any suitable tags, you can use --always.

git describe --always 

Answer 2

I have had this problem in a CI build environment where the CI tool was performing a shallow clone of the repository. This was frustrating, because in my development environment, the command

git describe --tags 

would give me output like

2.2.12-7-g8ec9d6c9 

whereas in the build environment I would get the "fatal no names found" error. If I tried using the --always tag

git describe --tags --always 

then I would simply get the hash of the latest commit, but not the most recent tag prior to that commit

8ec9d6c9 

Performing a git pull in the build environment wouldn't help, because once the repo has been cloned shallowly, future pulls will not update the tags.

The solution was to ensure that the initial clone of the repo in the build environment was not a shallow clone (i.e. the git clone command was not used with --depth, --shallow-since or --shallow-exclude parameters).