Merge branch 'nd/wildmatch-double-asterisk'

A pattern with '**' that does not have a slash on either side used
to be an invalid one, but the code now treats such double-asterisks
the same way as two normal asterisks that happen to be adjacent to
each other.

* nd/wildmatch-double-asterisk:
  wildmatch: change behavior of "foo**bar" in WM_PATHNAME mode

Documentation/gitignore.txt

@@ -129,7 +129,8 @@ full pathname may have special meaning:
    matches zero or more directories. For example, "`a/**/b`"
    matches "`a/b`", "`a/x/b`", "`a/x/y/b`" and so on.
 
- - Other consecutive asterisks are considered invalid.
+ - Other consecutive asterisks are considered regular asterisks and
+   will match according to the previous rules.
 
 NOTES
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