test-grep: add tests for --follow with/without --diff and/or paths

This tests the behavior of cmdutil.walkchangerevs().

I'm going to rewrite cmdutil.walkchangerevs() to leverage the "log -f"
logic, but the code coverage looked quite small. And the history traversal
of "grep -f" goes wrong in various ways.

tests/test-grep.t

@@ -1,815 +1,1331 b''
   $ hg init t
   $ cd t
   $ echo import > port
   $ hg add port
   $ hg commit -m 0 -u spam -d '0 0'
   $ echo export >> port
   $ hg commit -m 1 -u eggs -d '1 0'
   $ echo export > port
   $ echo vaportight >> port
   $ echo 'import/export' >> port
   $ hg commit -m 2 -u spam -d '2 0'
   $ echo 'import/export' >> port
   $ hg commit -m 3 -u eggs -d '3 0'
   $ head -n 3 port > port1
   $ mv port1 port
   $ hg commit -m 4 -u spam -d '4 0'
 
 pattern error
 
   $ hg grep '**test**'
   grep: invalid match pattern: nothing to repeat* (glob)
   [1]
 
 simple
 
   $ hg grep -r tip:0 '.*'
   port:4:export
   port:4:vaportight
   port:4:import/export
   port:3:export
   port:3:vaportight
   port:3:import/export
   port:3:import/export
   port:2:export
   port:2:vaportight
   port:2:import/export
   port:1:import
   port:1:export
   port:0:import
   $ hg grep -r tip:0 port port
   port:4:export
   port:4:vaportight
   port:4:import/export
   port:3:export
   port:3:vaportight
   port:3:import/export
   port:3:import/export
   port:2:export
   port:2:vaportight
   port:2:import/export
   port:1:import
   port:1:export
   port:0:import
 
 simple from subdirectory
 
   $ mkdir dir
   $ cd dir
   $ hg grep -r tip:0 port
   port:4:export
   port:4:vaportight
   port:4:import/export
   port:3:export
   port:3:vaportight
   port:3:import/export
   port:3:import/export
   port:2:export
   port:2:vaportight
   port:2:import/export
   port:1:import
   port:1:export
   port:0:import
   $ hg grep -r tip:0 port --config ui.relative-paths=yes
   ../port:4:export
   ../port:4:vaportight
   ../port:4:import/export
   ../port:3:export
   ../port:3:vaportight
   ../port:3:import/export
   ../port:3:import/export
   ../port:2:export
   ../port:2:vaportight
   ../port:2:import/export
   ../port:1:import
   ../port:1:export
   ../port:0:import
   $ cd ..
 
 simple with color
 
   $ hg --config extensions.color= grep --config color.mode=ansi \
   >     --color=always port port -r tip:0
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m4\x1b[0m\x1b[0;36m:\x1b[0mex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m4\x1b[0m\x1b[0;36m:\x1b[0mva\x1b[0;31;1mport\x1b[0might (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m4\x1b[0m\x1b[0;36m:\x1b[0mim\x1b[0;31;1mport\x1b[0m/ex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m3\x1b[0m\x1b[0;36m:\x1b[0mex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m3\x1b[0m\x1b[0;36m:\x1b[0mva\x1b[0;31;1mport\x1b[0might (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m3\x1b[0m\x1b[0;36m:\x1b[0mim\x1b[0;31;1mport\x1b[0m/ex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m3\x1b[0m\x1b[0;36m:\x1b[0mim\x1b[0;31;1mport\x1b[0m/ex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m2\x1b[0m\x1b[0;36m:\x1b[0mex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m2\x1b[0m\x1b[0;36m:\x1b[0mva\x1b[0;31;1mport\x1b[0might (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m2\x1b[0m\x1b[0;36m:\x1b[0mim\x1b[0;31;1mport\x1b[0m/ex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m1\x1b[0m\x1b[0;36m:\x1b[0mim\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m1\x1b[0m\x1b[0;36m:\x1b[0mex\x1b[0;31;1mport\x1b[0m (esc)
   \x1b[0;35mport\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m0\x1b[0m\x1b[0;36m:\x1b[0mim\x1b[0;31;1mport\x1b[0m (esc)
 
 simple templated
 
   $ hg grep port -r tip:0 \
   > -T '{path}:{rev}:{node|short}:{texts % "{if(matched, text|upper, text)}"}\n'
   port:4:914fa752cdea:exPORT
   port:4:914fa752cdea:vaPORTight
   port:4:914fa752cdea:imPORT/exPORT
   port:3:95040cfd017d:exPORT
   port:3:95040cfd017d:vaPORTight
   port:3:95040cfd017d:imPORT/exPORT
   port:3:95040cfd017d:imPORT/exPORT
   port:2:3b325e3481a1:exPORT
   port:2:3b325e3481a1:vaPORTight
   port:2:3b325e3481a1:imPORT/exPORT
   port:1:8b20f75c1585:imPORT
   port:1:8b20f75c1585:exPORT
   port:0:f31323c92170:imPORT
 
   $ hg grep port -r tip:0 -T '{path}:{rev}:{texts}\n'
   port:4:export
   port:4:vaportight
   port:4:import/export
   port:3:export
   port:3:vaportight
   port:3:import/export
   port:3:import/export
   port:2:export
   port:2:vaportight
   port:2:import/export
   port:1:import
   port:1:export
   port:0:import
 
   $ hg grep port -r tip:0 -T '{path}:{tags}:{texts}\n'
   port:tip:export
   port:tip:vaportight
   port:tip:import/export
   port::export
   port::vaportight
   port::import/export
   port::import/export
   port::export
   port::vaportight
   port::import/export
   port::import
   port::export
   port::import
 
 simple JSON (no "change" field)
 
   $ hg grep -r tip:0 -Tjson port
   [
    {
     "date": [4, 0],
     "lineno": 1,
     "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
     "path": "port",
     "rev": 4,
     "texts": [{"matched": false, "text": "ex"}, {"matched": true, "text": "port"}],
     "user": "spam"
    },
    {
     "date": [4, 0],
     "lineno": 2,
     "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
     "path": "port",
     "rev": 4,
     "texts": [{"matched": false, "text": "va"}, {"matched": true, "text": "port"}, {"matched": false, "text": "ight"}],
     "user": "spam"
    },
    {
     "date": [4, 0],
     "lineno": 3,
     "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
     "path": "port",
     "rev": 4,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
     "user": "spam"
    },
    {
     "date": [3, 0],
     "lineno": 1,
     "node": "95040cfd017d658c536071c6290230a613c4c2a6",
     "path": "port",
     "rev": 3,
     "texts": [{"matched": false, "text": "ex"}, {"matched": true, "text": "port"}],
     "user": "eggs"
    },
    {
     "date": [3, 0],
     "lineno": 2,
     "node": "95040cfd017d658c536071c6290230a613c4c2a6",
     "path": "port",
     "rev": 3,
     "texts": [{"matched": false, "text": "va"}, {"matched": true, "text": "port"}, {"matched": false, "text": "ight"}],
     "user": "eggs"
    },
    {
     "date": [3, 0],
     "lineno": 3,
     "node": "95040cfd017d658c536071c6290230a613c4c2a6",
     "path": "port",
     "rev": 3,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
     "user": "eggs"
    },
    {
     "date": [3, 0],
     "lineno": 4,
     "node": "95040cfd017d658c536071c6290230a613c4c2a6",
     "path": "port",
     "rev": 3,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
     "user": "eggs"
    },
    {
     "date": [2, 0],
     "lineno": 1,
     "node": "3b325e3481a1f07435d81dfdbfa434d9a0245b47",
     "path": "port",
     "rev": 2,
     "texts": [{"matched": false, "text": "ex"}, {"matched": true, "text": "port"}],
     "user": "spam"
    },
    {
     "date": [2, 0],
     "lineno": 2,
     "node": "3b325e3481a1f07435d81dfdbfa434d9a0245b47",
     "path": "port",
     "rev": 2,
     "texts": [{"matched": false, "text": "va"}, {"matched": true, "text": "port"}, {"matched": false, "text": "ight"}],
     "user": "spam"
    },
    {
     "date": [2, 0],
     "lineno": 3,
     "node": "3b325e3481a1f07435d81dfdbfa434d9a0245b47",
     "path": "port",
     "rev": 2,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
     "user": "spam"
    },
    {
     "date": [1, 0],
     "lineno": 1,
     "node": "8b20f75c158513ff5ac80bd0e5219bfb6f0eb587",
     "path": "port",
     "rev": 1,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}],
     "user": "eggs"
    },
    {
     "date": [1, 0],
     "lineno": 2,
     "node": "8b20f75c158513ff5ac80bd0e5219bfb6f0eb587",
     "path": "port",
     "rev": 1,
     "texts": [{"matched": false, "text": "ex"}, {"matched": true, "text": "port"}],
     "user": "eggs"
    },
    {
     "date": [0, 0],
     "lineno": 1,
     "node": "f31323c9217050ba245ee8b537c713ec2e8ab226",
     "path": "port",
     "rev": 0,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}],
     "user": "spam"
    }
   ]
 
 simple JSON without matching lines
 
   $ hg grep -r tip:0 -Tjson -l port
   [
    {
     "date": [4, 0],
     "lineno": 1,
     "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
     "path": "port",
     "rev": 4,
     "user": "spam"
    },
    {
     "date": [3, 0],
     "lineno": 1,
     "node": "95040cfd017d658c536071c6290230a613c4c2a6",
     "path": "port",
     "rev": 3,
     "user": "eggs"
    },
    {
     "date": [2, 0],
     "lineno": 1,
     "node": "3b325e3481a1f07435d81dfdbfa434d9a0245b47",
     "path": "port",
     "rev": 2,
     "user": "spam"
    },
    {
     "date": [1, 0],
     "lineno": 1,
     "node": "8b20f75c158513ff5ac80bd0e5219bfb6f0eb587",
     "path": "port",
     "rev": 1,
     "user": "eggs"
    },
    {
     "date": [0, 0],
     "lineno": 1,
     "node": "f31323c9217050ba245ee8b537c713ec2e8ab226",
     "path": "port",
     "rev": 0,
     "user": "spam"
    }
   ]
 
 diff of each revision for reference
 
   $ hg log -p -T'== rev: {rev} ==\n'
   == rev: 4 ==
   diff -r 95040cfd017d -r 914fa752cdea port
   --- a/port	Thu Jan 01 00:00:03 1970 +0000
   +++ b/port	Thu Jan 01 00:00:04 1970 +0000
   @@ -1,4 +1,3 @@
    export
    vaportight
    import/export
   -import/export
   
   == rev: 3 ==
   diff -r 3b325e3481a1 -r 95040cfd017d port
   --- a/port	Thu Jan 01 00:00:02 1970 +0000
   +++ b/port	Thu Jan 01 00:00:03 1970 +0000
   @@ -1,3 +1,4 @@
    export
    vaportight
    import/export
   +import/export
   
   == rev: 2 ==
   diff -r 8b20f75c1585 -r 3b325e3481a1 port
   --- a/port	Thu Jan 01 00:00:01 1970 +0000
   +++ b/port	Thu Jan 01 00:00:02 1970 +0000
   @@ -1,2 +1,3 @@
   -import
    export
   +vaportight
   +import/export
   
   == rev: 1 ==
   diff -r f31323c92170 -r 8b20f75c1585 port
   --- a/port	Thu Jan 01 00:00:00 1970 +0000
   +++ b/port	Thu Jan 01 00:00:01 1970 +0000
   @@ -1,1 +1,2 @@
    import
   +export
   
   == rev: 0 ==
   diff -r 000000000000 -r f31323c92170 port
   --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
   +++ b/port	Thu Jan 01 00:00:00 1970 +0000
   @@ -0,0 +1,1 @@
   +import
   
 
 all
 
   $ hg grep --traceback --all -nu port port
   port:4:4:-:spam:import/export
   port:3:4:+:eggs:import/export
   port:2:1:-:spam:import
   port:2:2:+:spam:vaportight
   port:2:3:+:spam:import/export
   port:1:2:+:eggs:export
   port:0:1:+:spam:import
 
 all JSON
 
   $ hg grep --all -Tjson port port
   [
    {
     "change": "-",
     "date": [4, 0],
     "lineno": 4,
     "node": "914fa752cdea87777ac1a8d5c858b0c736218f6c",
     "path": "port",
     "rev": 4,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
     "user": "spam"
    },
    {
     "change": "+",
     "date": [3, 0],
     "lineno": 4,
     "node": "95040cfd017d658c536071c6290230a613c4c2a6",
     "path": "port",
     "rev": 3,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
     "user": "eggs"
    },
    {
     "change": "-",
     "date": [2, 0],
     "lineno": 1,
     "node": "3b325e3481a1f07435d81dfdbfa434d9a0245b47",
     "path": "port",
     "rev": 2,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}],
     "user": "spam"
    },
    {
     "change": "+",
     "date": [2, 0],
     "lineno": 2,
     "node": "3b325e3481a1f07435d81dfdbfa434d9a0245b47",
     "path": "port",
     "rev": 2,
     "texts": [{"matched": false, "text": "va"}, {"matched": true, "text": "port"}, {"matched": false, "text": "ight"}],
     "user": "spam"
    },
    {
     "change": "+",
     "date": [2, 0],
     "lineno": 3,
     "node": "3b325e3481a1f07435d81dfdbfa434d9a0245b47",
     "path": "port",
     "rev": 2,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}, {"matched": false, "text": "/ex"}, {"matched": true, "text": "port"}],
     "user": "spam"
    },
    {
     "change": "+",
     "date": [1, 0],
     "lineno": 2,
     "node": "8b20f75c158513ff5ac80bd0e5219bfb6f0eb587",
     "path": "port",
     "rev": 1,
     "texts": [{"matched": false, "text": "ex"}, {"matched": true, "text": "port"}],
     "user": "eggs"
    },
    {
     "change": "+",
     "date": [0, 0],
     "lineno": 1,
     "node": "f31323c9217050ba245ee8b537c713ec2e8ab226",
     "path": "port",
     "rev": 0,
     "texts": [{"matched": false, "text": "im"}, {"matched": true, "text": "port"}],
     "user": "spam"
    }
   ]
 
 other
 
   $ hg grep -r tip:0 -l port port
   port:4
   port:3
   port:2
   port:1
   port:0
   $ hg grep -r tip:0 import port
   port:4:import/export
   port:3:import/export
   port:3:import/export
   port:2:import/export
   port:1:import
   port:0:import
 
   $ hg cp port port2
   $ hg commit -m 4 -u spam -d '5 0'
 
 follow
 
   $ hg grep -r tip:0 --traceback -f 'import\n\Z' port2
   [1]
   $ echo deport >> port2
   $ hg commit -m 5 -u eggs -d '6 0'
   $ hg grep -f --all -nu port port2
   port2:6:4:+:eggs:deport
   port:4:4:-:spam:import/export
   port:3:4:+:eggs:import/export
   port:2:1:-:spam:import
   port:2:2:+:spam:vaportight
   port:2:3:+:spam:import/export
   port:1:2:+:eggs:export
   port:0:1:+:spam:import
 
   $ hg up -q null
   $ hg grep -r 'reverse(:.)' -f port
   port:0:import
 
 Test wdir
 (at least, this shouldn't crash)
 
   $ hg up -q
   $ echo wport >> port2
   $ hg stat
   M port2
   $ hg grep -r 'wdir()' port
   port:2147483647:export
   port:2147483647:vaportight
   port:2147483647:import/export
   port2:2147483647:export
   port2:2147483647:vaportight
   port2:2147483647:import/export
   port2:2147483647:deport
   port2:2147483647:wport
 
   $ cd ..
   $ hg init t2
   $ cd t2
   $ hg grep -r tip:0 foobar foo
   [1]
   $ hg grep -r tip:0 foobar
   [1]
   $ echo blue >> color
   $ echo black >> color
   $ hg add color
   $ hg ci -m 0
   $ echo orange >> color
   $ hg ci -m 1
   $ echo black > color
   $ hg ci -m 2
   $ echo orange >> color
   $ echo blue >> color
   $ hg ci -m 3
   $ hg grep -r tip:0 orange
   color:3:orange
   color:1:orange
   $ hg grep --all orange
   color:3:+:orange
   color:2:-:orange
   color:1:+:orange
   $ hg grep --diff orange --color=debug
   [grep.filename|color][grep.sep|:][grep.rev|3][grep.sep|:][grep.inserted grep.change|+][grep.sep|:][grep.match|orange]
   [grep.filename|color][grep.sep|:][grep.rev|2][grep.sep|:][grep.deleted grep.change|-][grep.sep|:][grep.match|orange]
   [grep.filename|color][grep.sep|:][grep.rev|1][grep.sep|:][grep.inserted grep.change|+][grep.sep|:][grep.match|orange]
 
   $ hg grep --diff orange --color=yes
   \x1b[0;35mcolor\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m3\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;32;1m+\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;31;1morange\x1b[0m (esc)
   \x1b[0;35mcolor\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m2\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;31;1m-\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;31;1morange\x1b[0m (esc)
   \x1b[0;35mcolor\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;34m1\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;32;1m+\x1b[0m\x1b[0;36m:\x1b[0m\x1b[0;31;1morange\x1b[0m (esc)
 
   $ hg grep --diff orange
   color:3:+:orange
   color:2:-:orange
   color:1:+:orange
 
 test substring match: '^' should only match at the beginning
 
   $ hg grep -r tip:0 '^.' --config extensions.color= --color debug
   [grep.filename|color][grep.sep|:][grep.rev|3][grep.sep|:][grep.match|b]lack
   [grep.filename|color][grep.sep|:][grep.rev|3][grep.sep|:][grep.match|o]range
   [grep.filename|color][grep.sep|:][grep.rev|3][grep.sep|:][grep.match|b]lue
   [grep.filename|color][grep.sep|:][grep.rev|2][grep.sep|:][grep.match|b]lack
   [grep.filename|color][grep.sep|:][grep.rev|1][grep.sep|:][grep.match|b]lue
   [grep.filename|color][grep.sep|:][grep.rev|1][grep.sep|:][grep.match|b]lack
   [grep.filename|color][grep.sep|:][grep.rev|1][grep.sep|:][grep.match|o]range
   [grep.filename|color][grep.sep|:][grep.rev|0][grep.sep|:][grep.match|b]lue
   [grep.filename|color][grep.sep|:][grep.rev|0][grep.sep|:][grep.match|b]lack
 
 match in last "line" without newline
 
   $ "$PYTHON" -c 'fp = open("noeol", "wb"); fp.write(b"no infinite loop"); fp.close();'
   $ hg ci -Amnoeol
   adding noeol
   $ hg grep -r tip:0 loop
   noeol:4:no infinite loop
 
   $ cd ..
 
 Issue685: traceback in grep -r after rename
 
 Got a traceback when using grep on a single
 revision with renamed files.
 
   $ hg init issue685
   $ cd issue685
   $ echo octarine > color
   $ hg ci -Amcolor
   adding color
   $ hg rename color colour
   $ hg ci -Am rename
   $ hg grep -r tip:0 octarine
   colour:1:octarine
   color:0:octarine
 
 Used to crash here
 
   $ hg grep -r 1 octarine
   colour:1:octarine
   $ cd ..
 
 
 Issue337: test that grep follows parent-child relationships instead
 of just using revision numbers.
 
   $ hg init issue337
   $ cd issue337
 
   $ echo white > color
   $ hg commit -A -m "0 white"
   adding color
 
   $ echo red > color
   $ hg commit -A -m "1 red"
 
   $ hg update 0
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo black > color
   $ hg commit -A -m "2 black"
   created new head
 
   $ hg update --clean 1
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo blue > color
   $ hg commit -A -m "3 blue"
 
   $ hg grep --all red
   color:3:-:red
   color:1:+:red
 
   $ hg grep --diff red
   color:3:-:red
   color:1:+:red
 
 Issue3885: test that changing revision order does not alter the
 revisions printed, just their order.
 
   $ hg grep --all red -r "all()"
   color:1:+:red
   color:3:-:red
 
   $ hg grep --all red -r "reverse(all())"
   color:3:-:red
   color:1:+:red
 
   $ hg grep --diff red -r "all()"
   color:1:+:red
   color:3:-:red
 
   $ hg grep --diff red -r "reverse(all())"
   color:3:-:red
   color:1:+:red
 
   $ cd ..
 
   $ hg init a
   $ cd a
   $ cp "$TESTDIR/binfile.bin" .
   $ hg add binfile.bin
   $ hg ci -m 'add binfile.bin'
   $ hg grep "MaCam" --all
   binfile.bin:0:+: Binary file matches
 
   $ hg grep "MaCam" --diff
   binfile.bin:0:+: Binary file matches
 
   $ cd ..
 
 Moved line may not be collected by "grep --diff" since it first filters
 the contents to be diffed by the pattern. (i.e.
 "diff <(grep pat a) <(grep pat b)", not "diff a b | grep pat".)
 This is much faster than generating full diff per revision.
 
   $ hg init moved-line
   $ cd moved-line
   $ cat <<'EOF' > a
   > foo
   > bar
   > baz
   > EOF
   $ hg ci -Am initial
   adding a
   $ cat <<'EOF' > a
   > bar
   > baz
   > foo
   > EOF
   $ hg ci -m reorder
 
   $ hg diff -c 1
   diff -r a593cc55e81b -r 69789a3b6e80 a
   --- a/a	Thu Jan 01 00:00:00 1970 +0000
   +++ b/a	Thu Jan 01 00:00:00 1970 +0000
   @@ -1,3 +1,3 @@
   -foo
    bar
    baz
   +foo
 
  can't find the move of "foo" at the revision 1:
 
   $ hg grep --diff foo -r1
   [1]
 
  "bar" isn't moved at the revisoin 1:
 
   $ hg grep --diff bar -r1
   [1]
 
   $ cd ..
 
 Test for showing working of allfiles flag
 
   $ hg init sng
   $ cd sng
   $ echo "unmod" >> um
   $ echo old > old
   $ hg ci -q -A -m "adds unmod to um"
   $ echo "something else" >> new
   $ hg ci -A -m "second commit"
   adding new
   $ hg grep -r "." "unmod"
   um:1:unmod
 
 Existing tracked files in the working directory are searched by default
 
   $ echo modified >> new
   $ echo 'added' > added; hg add added
   $ echo 'added, missing' > added-missing; hg add added-missing; rm added-missing
   $ echo 'untracked' > untracked
   $ hg rm old
   $ hg grep ''
   added:added
   new:something else
   new:modified
   um:unmod
 
 #if symlink
 Grepping a symlink greps its destination
 
   $ rm -f added; ln -s symlink-added added
   $ hg grep '' | grep added
   added:symlink-added
 
 But we reject symlinks as directories components of a tracked file as
 usual:
 
   $ mkdir dir; touch dir/f; hg add dir/f
   $ rm -rf dir; ln -s / dir
   $ hg grep ''
   abort: path 'dir/f' traverses symbolic link 'dir'
   [255]
 #endif
 
 But we can search files from some other revision with -rREV
 
   $ hg grep -r. mod
   um:1:unmod
 
   $ hg grep --diff mod
   um:0:+:unmod
 
   $ cd ..
 
 Change Default of grep by ui.tweakdefaults, that is, the files not in current
 working directory should not be grepp-ed on
 
   $ hg init ab
   $ cd ab
   $ cat <<'EOF' >> .hg/hgrc
   > [ui]
   > tweakdefaults = True
   > EOF
   $ echo "some text">>file1
   $ hg add file1
   $ hg commit -m "adds file1"
   $ hg mv file1 file2
 
 wdir revision is hidden by default:
 
   $ hg grep "some"
   file2:some text
 
 but it should be available in template dict:
 
   $ hg grep "some" -Tjson
   [
    {
     "date": [0, 0],
     "lineno": 1,
     "node": "ffffffffffffffffffffffffffffffffffffffff",
     "path": "file2",
     "rev": 2147483647,
     "texts": [{"matched": true, "text": "some"}, {"matched": false, "text": " text"}],
     "user": "test"
    }
   ]
 
   $ cd ..
 
 test -rMULTIREV
 
   $ cd sng
   $ hg rm um
   $ hg commit -m "deletes um"
   $ hg grep -r "0:2" "unmod"
   um:0:unmod
   um:1:unmod
   $ hg grep -r "0:2" "unmod" um
   um:0:unmod
   um:1:unmod
   $ hg grep -r "0:2" "unmod" "glob:**/um" # Check that patterns also work
   um:0:unmod
   um:1:unmod
   $ cd ..
 
+--follow with/without --diff and/or paths
+-----------------------------------------
+
+For each test case, we compare the history traversal of "hg log",
+"hg grep --diff", and "hg grep" (--all-files).
+
+"hg grep --diff" should traverse the log in the same way as "hg log".
+"hg grep" (--all-files) is slightly different in that it includes
+unmodified changes.
+
+  $ hg init follow
+  $ cd follow
+
+  $ cat <<'EOF' >> .hg/hgrc
+  > [ui]
+  > logtemplate = '{rev}: {join(files % "{status} {path}", ", ")}\n'
+  > EOF
+
+  $ for f in add0 add0-mod1 add0-rm1 add0-mod2 add0-rm2 add0-mod3 add0-mod4 add0-rm4; do
+  > echo data0 >> $f
+  > done
+  $ hg ci -qAm0
+
+  $ hg cp add0 add0-cp1
+  $ hg cp add0 add0-cp1-mod1
+  $ hg cp add0 add0-cp1-mod1-rm3
+  $ hg rm add0-rm1
+  $ for f in *mod1*; do
+  > echo data1 >> $f
+  > done
+  $ hg ci -qAm1
+
+  $ hg update -q 0
+  $ hg cp add0 add0-cp2
+  $ hg cp add0 add0-cp2-mod2
+  $ hg rm add0-rm2
+  $ for f in *mod2*; do
+  > echo data2 >> $f
+  > done
+  $ hg ci -qAm2
+
+  $ hg update -q 1
+  $ hg cp add0-cp1 add0-cp1-cp3
+  $ hg cp add0-cp1-mod1 add0-cp1-mod1-cp3-mod3
+  $ hg rm add0-cp1-mod1-rm3
+  $ for f in *mod3*; do
+  > echo data3 >> $f
+  > done
+  $ hg ci -qAm3
+
+  $ hg cp add0 add0-cp4
+  $ hg cp add0 add0-cp4-mod4
+  $ hg rm add0-rm4
+  $ for f in *mod4*; do
+  > echo data4 >> $f
+  > done
+
+  $ hg log -Gr':wdir()'
+  o  2147483647: A add0-cp4, A add0-cp4-mod4, M add0-mod4, R add0-rm4
+  |
+  @  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  |
+  | o  2: A add0-cp2, A add0-cp2-mod2, M add0-mod2, R add0-rm2
+  | |
+  o |  1: A add0-cp1, A add0-cp1-mod1, A add0-cp1-mod1-rm3, M add0-mod1, R add0-rm1
+  |/
+  o  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+  
+
+follow revision history from wdir parent:
+
+  $ hg log -f
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  1: A add0-cp1, A add0-cp1-mod1, A add0-cp1-mod1-rm3, M add0-mod1, R add0-rm1
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+  $ hg grep --diff -f data
+  add0-cp1-mod1-cp3-mod3:3:+:data3
+  add0-mod3:3:+:data3
+  add0-cp1-mod1:1:+:data1
+  add0-cp1-mod1-rm3:1:+:data1
+  add0-mod1:1:+:data1
+  add0:0:+:data0
+  add0-mod1:0:+:data0
+  add0-mod2:0:+:data0
+  add0-mod3:0:+:data0
+  add0-mod4:0:+:data0
+  add0-rm1:0:+:data0
+  add0-rm2:0:+:data0
+  add0-rm4:0:+:data0
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data
+  add0:data0
+  add0-cp1:data0
+  add0-cp1-cp3:data0
+  add0-cp1-mod1:data0
+  add0-cp1-mod1:data1
+  add0-cp1-mod1-cp3-mod3:data0
+  add0-cp1-mod1-cp3-mod3:data1
+  add0-cp1-mod1-cp3-mod3:data3
+  add0-cp4:data0
+  add0-cp4-mod4:data0
+  add0-cp4-mod4:data4
+  add0-mod1:data0
+  add0-mod1:data1
+  add0-mod2:data0
+  add0-mod3:data0
+  add0-mod3:data3
+  add0-mod4:data0
+  add0-mod4:data4
+  add0-rm2:data0
+
+follow revision history from specified revision:
+
+  $ hg log -fr2
+  2: A add0-cp2, A add0-cp2-mod2, M add0-mod2, R add0-rm2
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+  $ hg grep --diff -fr2 data
+  add0-cp2-mod2:2:+:data2
+  add0-mod2:2:+:data2
+
+ BROKEN: should follow history
+  $ hg grep -fr2 data
+  add0:2:data0
+  add0-cp2:2:data0
+  add0-cp2-mod2:2:data0
+  add0-cp2-mod2:2:data2
+  add0-mod1:2:data0
+  add0-mod2:2:data0
+  add0-mod2:2:data2
+  add0-mod3:2:data0
+  add0-mod4:2:data0
+  add0-rm1:2:data0
+  add0-rm4:2:data0
+
+follow revision history from wdir:
+
+  $ hg log -fr'wdir()'
+  2147483647: A add0-cp4, A add0-cp4-mod4, M add0-mod4, R add0-rm4
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  1: A add0-cp1, A add0-cp1-mod1, A add0-cp1-mod1-rm3, M add0-mod1, R add0-rm1
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+ BROKEN: should not abort because of removed file
+  $ hg grep --diff -fr'wdir()' data
+  add0-cp4-mod4:2147483647:+:data4
+  add0-mod4:2147483647:+:data4
+  add0-rm4:2147483647:-:abort: add0-rm4@None: not found in manifest!
+  [255]
+
+ BROKEN: should follow history
+  $ hg grep -fr'wdir()' data
+  add0:2147483647:data0
+  add0-cp1:2147483647:data0
+  add0-cp1-cp3:2147483647:data0
+  add0-cp1-mod1:2147483647:data0
+  add0-cp1-mod1:2147483647:data1
+  add0-cp1-mod1-cp3-mod3:2147483647:data0
+  add0-cp1-mod1-cp3-mod3:2147483647:data1
+  add0-cp1-mod1-cp3-mod3:2147483647:data3
+  add0-cp4:2147483647:data0
+  add0-cp4-mod4:2147483647:data0
+  add0-cp4-mod4:2147483647:data4
+  add0-mod1:2147483647:data0
+  add0-mod1:2147483647:data1
+  add0-mod2:2147483647:data0
+  add0-mod3:2147483647:data0
+  add0-mod3:2147483647:data3
+  add0-mod4:2147483647:data0
+  add0-mod4:2147483647:data4
+  add0-rm2:2147483647:data0
+
+follow revision history from multiple revisions:
+
+  $ hg log -fr'1+2'
+  2: A add0-cp2, A add0-cp2-mod2, M add0-mod2, R add0-rm2
+  1: A add0-cp1, A add0-cp1-mod1, A add0-cp1-mod1-rm3, M add0-mod1, R add0-rm1
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+ BROKEN: should include the revision 2
+  $ hg grep --diff -fr'1+2' data
+  add0-cp1-mod1:1:+:data1
+  add0-cp1-mod1-rm3:1:+:data1
+  add0-mod1:1:+:data1
+
+ BROKEN: should follow history
+ BROKEN: should include the revision 2
+  $ hg grep -fr'1+2' data
+  add0:1:data0
+  add0-cp1:1:data0
+  add0-cp1-mod1:1:data0
+  add0-cp1-mod1:1:data1
+  add0-cp1-mod1-rm3:1:data0
+  add0-cp1-mod1-rm3:1:data1
+  add0-mod1:1:data0
+  add0-mod1:1:data1
+  add0-mod2:1:data0
+  add0-mod3:1:data0
+  add0-mod4:1:data0
+  add0-rm2:1:data0
+  add0-rm4:1:data0
+
+follow file history from wdir parent, unmodified in wdir:
+
+  $ hg log -f add0-mod3
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+  $ hg grep --diff -f data add0-mod3
+  add0-mod3:3:+:data3
+  add0-mod3:0:+:data0
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-mod3
+  add0-mod3:data0
+  add0-mod3:data3
+
+follow file history from wdir parent, modified in wdir:
+
+  $ hg log -f add0-mod4
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+  $ hg grep --diff -f data add0-mod4
+  add0-mod4:0:+:data0
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-mod4
+  add0-mod4:data0
+  add0-mod4:data4
+
+follow file history from wdir parent, copied but unmodified:
+
+  $ hg log -f add0-cp1-cp3
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  1: A add0-cp1, A add0-cp1-mod1, A add0-cp1-mod1-rm3, M add0-mod1, R add0-rm1
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+  $ hg grep --diff -f data add0-cp1-cp3
+  add0:0:+:data0
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-cp1-cp3
+  add0-cp1-cp3:data0
+
+follow file history from wdir parent, copied and modified:
+
+  $ hg log -f add0-cp1-mod1-cp3-mod3
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  1: A add0-cp1, A add0-cp1-mod1, A add0-cp1-mod1-rm3, M add0-mod1, R add0-rm1
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+  $ hg grep --diff -f data add0-cp1-mod1-cp3-mod3
+  add0-cp1-mod1-cp3-mod3:3:+:data3
+  add0-cp1-mod1:1:+:data1
+  add0:0:+:data0
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-cp1-mod1-cp3-mod3
+  add0-cp1-mod1-cp3-mod3:data0
+  add0-cp1-mod1-cp3-mod3:data1
+  add0-cp1-mod1-cp3-mod3:data3
+
+follow file history from wdir parent, copied in wdir:
+
+  $ hg log -f add0-cp4
+  abort: cannot follow nonexistent file: "add0-cp4"
+  [255]
+
+  $ hg grep --diff -f data add0-cp4
+  abort: cannot follow file not in parent revision: "add0-cp4"
+  [255]
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-cp4
+  add0-cp4:data0
+
+follow file history from wdir parent, removed:
+
+  $ hg log -f add0-cp1-mod1-rm3
+  abort: cannot follow file not in parent revision: "add0-cp1-mod1-rm3"
+  [255]
+
+  $ hg grep --diff -f data add0-cp1-mod1-rm3
+  abort: cannot follow file not in parent revision: "add0-cp1-mod1-rm3"
+  [255]
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-cp1-mod1-rm3
+  [1]
+
+follow file history from wdir parent (explicit), removed:
+
+  $ hg log -fr. add0-cp1-mod1-rm3
+  abort: cannot follow file not in any of the specified revisions: "add0-cp1-mod1-rm3"
+  [255]
+
+  $ hg grep --diff -fr. data add0-cp1-mod1-rm3
+  abort: cannot follow file not in parent revision: "add0-cp1-mod1-rm3"
+  [255]
+
+ BROKEN: should abort
+  $ hg grep -fr. data add0-cp1-mod1-rm3
+  [1]
+
+follow file history from wdir parent, removed in wdir:
+
+  $ hg log -f add0-rm4
+  abort: cannot follow file not in parent revision: "add0-rm4"
+  [255]
+
+ BROKEN: may be okay, but different behavior from "hg log"
+  $ hg grep --diff -f data add0-rm4
+  add0-rm4:0:+:data0
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-rm4
+  [1]
+
+follow file history from wdir parent (explicit), removed in wdir:
+
+  $ hg log -fr. add0-rm4
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+  $ hg grep --diff -fr. data add0-rm4
+  [1]
+
+ BROKEN: should follow history
+  $ hg grep -fr. data add0-rm4
+  add0-rm4:3:data0
+
+follow file history from wdir parent, multiple files:
+
+  $ hg log -f add0-mod3 add0-cp1-mod1
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  1: A add0-cp1, A add0-cp1-mod1, A add0-cp1-mod1-rm3, M add0-mod1, R add0-rm1
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+  $ hg grep --diff -f data add0-mod3 add0-cp1-mod1
+  add0-mod3:3:+:data3
+  add0-cp1-mod1:1:+:data1
+  add0:0:+:data0
+  add0-mod3:0:+:data0
+
+ BROKEN: should not fall back to plain grep
+  $ hg grep -f data add0-mod3 add0-cp1-mod1
+  add0-cp1-mod1:data0
+  add0-cp1-mod1:data1
+  add0-mod3:data0
+  add0-mod3:data3
+
+follow file history from specified revision, modified:
+
+  $ hg log -fr2 add0-mod2
+  2: A add0-cp2, A add0-cp2-mod2, M add0-mod2, R add0-rm2
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history from the specified revision
+  $ hg grep --diff -fr2 data add0-mod2
+  [1]
+
+ BROKEN: should follow history
+  $ hg grep -fr2 data add0-mod2
+  add0-mod2:2:data0
+  add0-mod2:2:data2
+
+follow file history from specified revision, copied but unmodified:
+
+  $ hg log -fr2 add0-cp2
+  2: A add0-cp2, A add0-cp2-mod2, M add0-mod2, R add0-rm2
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history from the specified revision
+  $ hg grep --diff -fr2 data add0-cp2
+  abort: cannot follow file not in parent revision: "add0-cp2"
+  [255]
+
+ BROKEN: should follow history across renames
+  $ hg grep -fr2 data add0-cp2
+  add0-cp2:2:data0
+
+follow file history from specified revision, copied and modified:
+
+  $ hg log -fr2 add0-cp2-mod2
+  2: A add0-cp2, A add0-cp2-mod2, M add0-mod2, R add0-rm2
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history from the specified revision
+  $ hg grep --diff -fr2 data add0-cp2-mod2
+  abort: cannot follow file not in parent revision: "add0-cp2-mod2"
+  [255]
+
+ BROKEN: should follow history across renames
+  $ hg grep -fr2 data add0-cp2-mod2
+  add0-cp2-mod2:2:data0
+  add0-cp2-mod2:2:data2
+
+follow file history from specified revision, removed:
+
+  $ hg log -fr2 add0-rm2
+  abort: cannot follow file not in any of the specified revisions: "add0-rm2"
+  [255]
+
+ BROKEN: should abort
+  $ hg grep --diff -fr2 data add0-rm2
+  [1]
+
+ BROKEN: should abort
+  $ hg grep -fr2 data add0-rm2
+  [1]
+
+follow file history from specified revision, multiple files:
+
+  $ hg log -fr2 add0-cp2 add0-mod2
+  2: A add0-cp2, A add0-cp2-mod2, M add0-mod2, R add0-rm2
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history from the specified revision
+  $ hg grep --diff -fr2 data add0-cp2 add0-mod2
+  abort: cannot follow file not in parent revision: "add0-cp2"
+  [255]
+
+ BROKEN: should follow history
+  $ hg grep -fr2 data add0-cp2 add0-mod2
+  add0-cp2:2:data0
+  add0-mod2:2:data0
+  add0-mod2:2:data2
+
+follow file history from wdir, unmodified:
+
+  $ hg log -fr'wdir()' add0-mod3
+  2147483647: A add0-cp4, A add0-cp4-mod4, M add0-mod4, R add0-rm4
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+  $ hg grep --diff -fr'wdir()' data add0-mod3
+  [1]
+
+ BROKEN: should follow history
+  $ hg grep -fr'wdir()' data add0-mod3
+  add0-mod3:2147483647:data0
+  add0-mod3:2147483647:data3
+
+follow file history from wdir, modified:
+
+  $ hg log -fr'wdir()' add0-mod4
+  2147483647: A add0-cp4, A add0-cp4-mod4, M add0-mod4, R add0-rm4
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history and show the changes in wdir
+  $ hg grep --diff -fr'wdir()' data add0-mod4
+  [1]
+
+ BROKEN: should follow history
+  $ hg grep -fr'wdir()' data add0-mod4
+  add0-mod4:2147483647:data0
+  add0-mod4:2147483647:data4
+
+follow file history from wdir, copied but unmodified:
+
+  $ hg log -fr'wdir()' add0-cp4
+  2147483647: A add0-cp4, A add0-cp4-mod4, M add0-mod4, R add0-rm4
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+  $ hg grep --diff -fr'wdir()' data add0-cp4
+  abort: cannot follow file not in parent revision: "add0-cp4"
+  [255]
+
+ BROKEN: should follow history across renames
+  $ hg grep -fr'wdir()' data add0-cp4
+  add0-cp4:2147483647:data0
+
+follow file history from wdir, copied and modified:
+
+  $ hg log -fr'wdir()' add0-cp4-mod4
+  2147483647: A add0-cp4, A add0-cp4-mod4, M add0-mod4, R add0-rm4
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+  $ hg grep --diff -fr'wdir()' data add0-cp4-mod4
+  abort: cannot follow file not in parent revision: "add0-cp4-mod4"
+  [255]
+
+ BROKEN: should follow history across renames
+  $ hg grep -fr'wdir()' data add0-cp4-mod4
+  add0-cp4-mod4:2147483647:data0
+  add0-cp4-mod4:2147483647:data4
+
+follow file history from wdir, multiple files:
+
+  $ hg log -fr'wdir()' add0-cp4 add0-mod4 add0-mod3
+  2147483647: A add0-cp4, A add0-cp4-mod4, M add0-mod4, R add0-rm4
+  3: A add0-cp1-cp3, A add0-cp1-mod1-cp3-mod3, R add0-cp1-mod1-rm3, M add0-mod3
+  0: A add0, A add0-mod1, A add0-mod2, A add0-mod3, A add0-mod4, A add0-rm1, A add0-rm2, A add0-rm4
+
+ BROKEN: should follow history
+  $ hg grep --diff -fr'wdir()' data add0-cp4 add0-mod4 add0-mod3
+  abort: cannot follow file not in parent revision: "add0-cp4"
+  [255]
+
+ BROKEN: should follow history
+  $ hg grep -fr'wdir()' data add0-cp4 add0-mod4 add0-mod3
+  add0-cp4:2147483647:data0
+  add0-mod3:2147483647:data0
+  add0-mod3:2147483647:data3
+  add0-mod4:2147483647:data0
+  add0-mod4:2147483647:data4
+
+  $ cd ..