I'm trying to get git-http-backend working on my remote vps with no luck. I've adjusted httpd.conf in a way similar to the on this question, but as soon as I add the ScriptAlias directive, the error occurs.
Apache error log:
suexec policy violation: see suexec log for more details
Premature end of script headers: git-http-backend
error: target uid/gid (503/500) mismatch with directory (0/0) or program (0/0) or trusted user (0/10)
I had this error while setting up moinmoin. I suspect it's both lines you need to pay attention to (which in my case, were):
[2014-09-18 17:17:18]: uid: (1009/testsite) gid: (1006/testsite) cmd: moin.cgi [2014-09-18 17:17:18]: target uid/gid (1009/1006) mismatch with directory (0/0) or program (0/0)
The first line is stating that a process - in this case owned by testsite:testsite - is attempting to execute a command (moin.cgi).
It then checks the calling process's user id/group id to see if it matches the command to be executed, which triggers the second output when it fails (0/0 indicates root/root).
Simply calling chown should fix it:
chown -R testsite:testsite </path/to/directory-or-binary>