grep: extract main search loop as searcher method

Still displayer part is in commands.grep(), the core grep logic is now
reusable. I'll revisit the displayer stuff later since it will be another
long series.

mercurial/commands.py

@@ -3403,8 +3403,6 b' def grep(ui, repo, pattern, *pats, **opt'
     )
 
     getfile = searcher._getfile
-    matches = searcher._matches
-    copies = searcher._copies
 
     uipathfn = scmutil.getuipathfn(repo)
 
@@ -3514,8 +3512,6 b' def grep(ui, repo, pattern, *pats, **opt'
             fm.data(matched=False)
         fm.end()
 
-    skip = searcher._skip
-    revfiles = searcher._revfiles
     found = False
 
     wopts = logcmdutil.walkopts(
@@ -3532,29 +3528,11 b' def grep(ui, repo, pattern, *pats, **opt'
 
     ui.pager(b'grep')
     fm = ui.formatter(b'grep', opts)
-    for ctx in scmutil.walkchangerevs(
-        repo, revs, makefilematcher, searcher._prep
-    ):
-        rev = ctx.rev()
-        parent = ctx.p1().rev()
-        for fn in sorted(revfiles.get(rev, [])):
-            states = matches[rev][fn]
-            copy = copies.get(rev, {}).get(fn)
-            if fn in skip:
-                if copy:
-                    skip.add(copy)
-                continue
-            pstates = matches.get(parent, {}).get(copy or fn, [])
-            if pstates or states:
-                r = display(fm, fn, ctx, pstates, states)
-                found = found or r
-                if r and not diff and not all_files:
-                    searcher.skipfile(fn, rev)
-        del revfiles[rev]
-        # We will keep the matches dict for the duration of the window
-        # clear the matches dict once the window is over
-        if not revfiles:
-            matches.clear()
+    for fn, ctx, pstates, states in searcher.searchfiles(revs, makefilematcher):
+        r = display(fm, fn, ctx, pstates, states)
+        found = found or r
+        if r and not diff and not all_files:
+            searcher.skipfile(fn, ctx.rev())
     fm.end()
 
     return not found

mercurial/grep.py

@@ -115,6 +115,34 b' class grepsearcher(object):'
         if copy:
             self._skip.add(copy)
 
+    def searchfiles(self, revs, makefilematcher):
+        """Walk files and revisions to yield (fn, ctx, pstates, states)
+        matches
+
+        states is a list of linestate objects. pstates may be empty unless
+        diff is True.
+        """
+        for ctx in scmutil.walkchangerevs(
+            self._repo, revs, makefilematcher, self._prep
+        ):
+            rev = ctx.rev()
+            parent = ctx.p1().rev()
+            for fn in sorted(self._revfiles.get(rev, [])):
+                states = self._matches[rev][fn]
+                copy = self._copies.get(rev, {}).get(fn)
+                if fn in self._skip:
+                    if copy:
+                        self._skip.add(copy)
+                    continue
+                pstates = self._matches.get(parent, {}).get(copy or fn, [])
+                if pstates or states:
+                    yield fn, ctx, pstates, states
+            del self._revfiles[rev]
+            # We will keep the matches dict for the duration of the window
+            # clear the matches dict once the window is over
+            if not self._revfiles:
+                self._matches.clear()
+
     def _grepbody(self, fn, rev, body):
         self._matches[rev].setdefault(fn, [])
         m = self._matches[rev][fn]