[ignore rules] fix for backslash handling

An attempt to re-implement not well documented Git CLI behavior for
patterns with backslashes.

It looks like Git silently ignores all \ characters in ignore rules, if
they are NOT covered by 3 cases described in [1]:

{quote}
1) ... Put a backslash ("\") in front of the first hash for patterns
that begin with a hash.
...
2) Trailing spaces are ignored unless they are quoted with backslash
("\").
...
3) Put a backslash ("\") in front of the first "!" for patterns that
begin with a literal "!", for example, "\!important!.txt".
{quote}

Undocumented also is the fact that backslash itself can be escaped by
backslash.

So \h\e\l\l\o\.t\x\t rule matches hello.txt and a\\\\b a\b in Git CLI.

Additionally, the glob parser [2] knows special meaning of backslash:

{quote}
One can remove the special meaning of '?', '*' and '[' by preceding
them by a backslash, or, in case this is part of a shell command
line, enclosing them in quotes.  Between brackets these characters
stand for themselves.  Thus, "[[?*\]" matches the four characters
'[', '?', '*' and '\'.
{quote}

[1] https://www.kernel.org/pub/software/scm/git/docs/gitignore.html
[2] http://man7.org/linux/man-pages/man7/glob.7.html

Bug: 478065
Change-Id: I3dc973475d1943c5622103701fa8cb3ea0684e3e
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

0 files changed, 0 insertions, 0 deletions