tweak ignore files

.gitignore

@@ -7,8 +7,10 @@ edit-git-bash.exe
 /git-extra/src/
 /git-extra/git-extra-*.pkg.tar.xz
 /git-shell/root/VERSION
+/git-shell/root/LICENSE.txt
 /git-shell/root/post-install.bat
 /git-shell/root/etc/
+/git-shell/root/mingw32/
 /git-extra/git-extra-*.src.tar.gz
 /installer/ReleaseNotes.html
 /installer/config.iss