For years we have used svn and are in the process of migrating all of our repositories to git. Part of this migration process was then setting up a webhook within Github to then update our local repositories in Redmine when a change was pushed. In order to handle that – I installed and configured the Redmine GitHub Hook plugin. When testing out the initial webhook – I kept getting the following error:
GithubHook: Command 'git fetch origin' didn't exit properly. Full output: ["error: cannot open FETCH_HEAD: Permission denied\n"]

In order to fix that error – there is another step needed in the set up process documented in Redmine GitHub Hook plugin Readme (Step 2: Add the repository to Redmine)

If you get the same error after following this step: HowTo keep in sync your git repository for redmine try this:

chmod 777 -R project.git

The entire process would then be:
(Note: In the below examples, “git_user” and “project.git” should be modified for your GitHub project)

1. git clone --mirror git@github.com:git_user/project.git
2. cd project.git
3. git fetch -q --all -p
4. chmod 777 -R project.git (make sure you are have moved outside of the project.git directory first)

That will then update as need without giving the permission denied error.