Add a / to the beginning of a file matchin pattern if no / in rule.

See https://www.kernel.org/pub/software/scm/git/docs/gitignore.html
Update custom-installers.md

Fixed documentation error.
Add prefer-stable flag to pick stable package over unstable ones when possible
Add prefer-stable docs
Merge pull request #1740 from Seldaek/preferstable

Add prefer-stable flag to pick stable package over unstable ones when possible
Merge pull request #1760 from gammamatrix/master

Documentation error: Replaced bad character
Add note about package naming in VCS repos/fork, fixes #1761
Update 02-libraries.md

Missing word
Merge pull request #1764 from simonpaarlberg/patch-1

Update 02-libraries.md
Merge pull request #1754 from njam/issue-1754

Fix file pattern start matching if no slash
Fix normalization of relative paths going up a few dirs, fixes #1759
Fix undef var issue when removing a json config key
Add composer diag command to diagnose problems automatically
Add docs for diag command
Moving svn driver to the last position as it causes conflicts with hg over http
Rename diag to diagnose, fix feedback
Merge branch 'diag'
Add a couple version parser tests
Fix dependency flags not applying to provides/replaces, fixes #1771
Fix normalization of relative paths