Thread:Project:Support desk/Can not recognize git and diff3 on system/reply (2)

Perhaps php isn't allowed to read files outside of its base directory, or otherwise cannot access the files in /usr/bin. By default the installer checks for the executables in the paths '/usr/bin', '/usr/local/bin', '/opt/csw/bin', '/usr/gnu/bin', '/usr/sfw/bin', '/sw/bin', and '/opt/local/bin'

You can always set the location of git and diff3 manually by setting $wgDiff3 and $wgGitBin (git is not very important - its only used to display the version hash on Special:Version if you're running directly off of a git checkout, diff3 is important for resolving edit conflicts)