Update scmgit to 1.7.0.7.

Update scmgit to 1.7.0.7.

This fixes http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-2542.

Changes since 1.7.0.5:
 * "git diff --stat" used "int" to count the size of differences,
   which could result in overflowing.
 * "git rev-list --abbrev-commit" defaulted to 40-byte abbreviations, unlike
   newer tools in the git toolset.
 * "make NO_CURL=NoThanks install" was broken.
 * An overlong line after ".gitdir: " in a git file caused out of bounds
   access to an array on the stack.
 * "git config --path conf.var" to attempt to expand a variable conf.var
   that uses "~/" short-hand segfaulted when $HOME environment variable
   was not set.