commands.debugrevlog: report max chain length

This is sometimes useful to know. Report it.

tests/test-debugcommands.t

@@ -1,96 +1,97 b''
   $ hg init debugrevlog
   $ cd debugrevlog
   $ echo a > a
   $ hg ci -Am adda
   adding a
   $ hg debugrevlog -m
   format : 1
   flags  : inline
   
   revisions     :  1
       merges    :  0 ( 0.00%)
       normal    :  1 (100.00%)
   revisions     :  1
       full      :  1 (100.00%)
       deltas    :  0 ( 0.00%)
   revision size : 44
       full      : 44 (100.00%)
       deltas    :  0 ( 0.00%)
   
   avg chain length  : 0
+  max chain length  : 0
   compression ratio : 0
   
   uncompressed data size (min/max/avg) : 43 / 43 / 43
   full revision size (min/max/avg)     : 44 / 44 / 44
   delta size (min/max/avg)             : 0 / 0 / 0
 
 Test debugindex, with and without the --debug flag
   $ hg debugindex a
      rev    offset  length   .... linkrev nodeid       p1           p2 (re)
        0         0       3   ....       0 b789fdd96dc2 000000000000 000000000000 (re)
   $ hg --debug debugindex a
      rev    offset  length   .... linkrev nodeid                                   p1                                       p2 (re)
        0         0       3   ....       0 b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000 (re)
   $ hg debugindex -f 1 a
      rev flag   offset   length     size   ....   link     p1     p2       nodeid (re)
        0 0000        0        3        2   ....      0     -1     -1 b789fdd96dc2 (re)
   $ hg --debug debugindex -f 1 a
      rev flag   offset   length     size   ....   link     p1     p2                                   nodeid (re)
        0 0000        0        3        2   ....      0     -1     -1 b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 (re)
 
 
 Test max chain len
   $ cat >> $HGRCPATH << EOF
   > [format]
   > maxchainlen=4
   > EOF
 
   $ printf "This test checks if maxchainlen config value is respected also it can serve as basic test for debugrevlog -d <file>.\n" >> a
   $ hg ci -m a
   $ printf "b\n" >> a
   $ hg ci -m a
   $ printf "c\n" >> a
   $ hg ci -m a
   $ printf "d\n" >> a
   $ hg ci -m a
   $ printf "e\n" >> a
   $ hg ci -m a
   $ printf "f\n" >> a
   $ hg ci -m a
   $ printf 'g\n' >> a
   $ hg ci -m a
   $ printf 'h\n' >> a
   $ hg ci -m a
   $ hg debugrevlog -d a
   # rev p1rev p2rev start   end deltastart base   p1   p2 rawsize totalsize compression heads chainlen
       0    -1    -1     0   ???          0    0    0    0     ???      ????           ?     1        0 (glob)
       1     0    -1   ???   ???          0    0    0    0     ???      ????           ?     1        1 (glob)
       2     1    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        2 (glob)
       3     2    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        3 (glob)
       4     3    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        4 (glob)
       5     4    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        0 (glob)
       6     5    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        1 (glob)
       7     6    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        2 (glob)
       8     7    -1   ???   ???        ???  ???  ???    0     ???      ????           ?     1        3 (glob)
   $ cd ..
 
 Test internal debugstacktrace command
 
   $ cat > debugstacktrace.py << EOF
   > from mercurial.util import debugstacktrace, dst, sys
   > def f():
   >     dst('hello world')
   > def g():
   >     f()
   >     debugstacktrace(skip=-5, f=sys.stdout)
   > g()
   > EOF
   $ python debugstacktrace.py
   hello world at:
    debugstacktrace.py:7 in * (glob)
    debugstacktrace.py:5 in g
    debugstacktrace.py:3 in f
   stacktrace at:
    debugstacktrace.py:7 *in * (glob)
    debugstacktrace.py:6 *in g (glob)
    */util.py:* in debugstacktrace (glob)