Git .gitignore rules

The rules are defined in http://git-scm.com/docs/gitignore
I won’t repeat them here, nor test them all. I will only explore some corner cases, not well explained in the said document…

Test

List all candidates to tracking with git status -u.
x means ‘shown by status’, empty means ‘ignored’.

	foo	/foo	foo/	f*	f*/	*.y	foo/c.x	foo/*.y	**/foo/*.y
bar/b.y	x	x	x	x	x		x	x	?
bar/foo/a.y		x					x	x?
bar/foo/c.x		x				x	?	x	?
bar/foo/d.y		x					x	x?
baz/f.y	x	x	x		x		x	x	?
baz/foo		x	x		x	x	x	x	?
baz/nf.x	x	x	x	x	x	x	x	x	x
foo/a.x						x	x	x	x
foo/b.y							x
foo/c.x						x		x	x

A bit surprised by the foo/c.x and foo/*.y patterns, I can’t see in the doc where they say that a pattern with slash and joker is anchored to top.
The last one is probably barely legal. One should keep things simple…
Now, let’s see the combination of exclude and re-include.

	foo	bar(1)	bar	bar/*	bar/foo/*	bar/foo/*
	!bar/foo	!bar/foo	!bar/foo/*	!bar/foo	!bar/foo/c.x	!bar/foo/*.y
bar/b.y	x		x?		x	x
bar/foo/a.y			x	x		x
bar/foo/c.x			x	x	x
bar/foo/d.y			x	x		x
baz/f.y	x	x	x	x	x	x
baz/foo		x	x	x	x	x
baz/nf.x	x	x	x	x	x	x
foo/a.x		x		x	x	x
foo/b.y		x		x	x	x
foo/c.x		x		x	x	x

(1) and /bar and bar/

I was confused by the re-include behavior, the post at http://stackoverflow.com/questions/2820255/how-do-negated-patterns-work-in-gitignore clarified the issue.
We need to add a joker to the exclude path so that re-include paths are examined.
Recursively:

	bar/*	bar/foo/*	bar/foo/*	bar/*	bar/foo/*
	!bar/foo	!bar/foo/c.x	!bar/foo/*.y (2)	!bar/foo	!bar/foo/*.y
				bar/foo/*	!bar/foo/zab/
				!bar/foo/zab	bar/foo/zab/*
					!bar/foo/zab/*.y
bar/b.y		x	x		x
bar/foo/a.y	x		x		x
bar/foo/c.x	x	x
bar/foo/d.y	x		x		x
bar/foo/zab/e.x	x	x		x
bar/foo/zab/f.y	x			x	x

(2) and !bar/foo/**/*.y and !bar/foo/zab/*.y