Git.pm: Make _temp_cache use the repository directory

Git.pm: Make _temp_cache use the repository directory

Update the usage of File::Temp->tempfile to place the temporary files
within the repository directory instead of just letting Perl decide what
directory to use, given there is a repository specified when requesting
the temporary file.

This is needed to be able to fix git-svn on msys as msysperl generates
paths with UNIX-style paths (/tmp/xxx) while the git tools expect natvie
path format (c:/..). The repository dir is stored in native format so by
using it as the base directory for temporary files we always get a
usable native full path.

Signed-off-by: Marten Svanfeldt <developer@svanfeldt.com>
Acked-by: Eric Wong <normalperson@yhbt.net>