git version 2.4.0
From https://github.com/curl/curl
 * branch            master     -> FETCH_HEAD
fatal: Unable to create '/export/home/buildbot/slave/curl-ares-solaris10-i386/build/.git/index.lock': File exists.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.