Add: (path) predicate

README.org

@@ -213,6 +213,7 @@ Arguments are listed next to predicate names, where applicable.
 +  ~habit~ :: Return non-nil if entry is a habit.
 +  ~heading (&rest regexps)~ :: Return non-nil if current entry's heading matches all ~REGEXPS~ (regexp strings).
 +  ~level (level-or-comparator &optional level)~ :: Return non-nil if current heading's outline level matches arguments.  The following forms are accepted: ~(level NUMBER)~: Matches if heading level is ~NUMBER~.  ~(level NUMBER NUMBER)~: Matches if heading level is equal to or between NUMBERs.  ~(level COMPARATOR NUMBER)~: Matches if heading level compares to ~NUMBER~ with ~COMPARATOR~.  ~COMPARATOR~ may be ~<~, ~<=~, ~>~, or ~>=~.
++  =path (&rest regexps)= :: Return non-nil if current heading's buffer's filename path matches any of =REGEXPS= (regexp strings).  Without arguments, return non-nil if buffer is file-backed.
 +  ~priority (&optional comparator-or-priority priority)~ :: Return non-nil if current heading has a certain priority.  ~COMPARATOR-OR-PRIORITY~ should be either a comparator function, like ~<=~, or a priority string, like "A" (in which case (~=~ will be the comparator).  If ~COMPARATOR-OR-PRIORITY~ is a comparator, ~PRIORITY~ should be a priority string.  If both arguments are nil, return non-nil if heading has any defined priority.
 +  ~property (property &optional value)~ :: Return non-nil if current entry has ~PROPERTY~ (a string), and optionally ~VALUE~ (a string).  Note that property inheritance is currently /not/ enabled for this predicate.  If you need to test with inheritance, you could use a custom predicate form, like ~(org-entry-get (point) "PROPERTY" 'inherit)~.
 +  ~regexp (regexp)~ :: Return non-nil if current entry matches ~REGEXP~ (a regexp string).  Matches against entire entry, from beginning of its heading to the next heading.
@@ -468,6 +469,7 @@ Expands into a call to ~org-ql-select~ with the same arguments.  For convenience
      -  For heading-local tags: =tags-local=, =local-tags=, =tags-l=, =ltags=.
      -  =tags-all=, =tags&=: Matches all given tags using boolean =AND= (rather than boolean =OR=, which the =tags= predicate uses).
 +  Variable =org-ql-block-header=, which overrides the default header in =org-ql-block= agenda blocks.
++  Predicate =(path)=.
 
 *Changed*
 +  Predicate =heading= now accepts multiple regexps, which are matched with boolean =AND=.