log-style: add a log style that is default+phase (issue3436)

There is a new style called phases style.
Usage::
    hg log --style phases

Why do we need this new style - in what way is it different from or similar to
existing styles?
The new style is default + phases information. With the new phases feature the
users exhibited their desire for a new style that could help them.

Why do this need a new style - couldn't it be folded into an existing style?
The default style and the new one are about the same, the difference is the
phases tag. The users find both styles useful, this means that the both styles
must exist.

mercurial/help/templates.txt

@@ -6,8 +6,8 b' template-style (--style).'
 You can customize output for any "log-like" command: log,
 outgoing, incoming, tip, parents, heads and glog.
 
-Four styles are packaged with Mercurial: default (the style used
-when no explicit preference is passed), compact, changelog,
+Five styles are packaged with Mercurial: default (the style used
+when no explicit preference is passed), compact, changelog, phases
 and xml.
 Usage::
 

mercurial/templates/map-cmdline.phases

@@ -1,4 +1,4 b''
-changeset = 'changeset:   {rev}:{node|short}\n{branches}{bookmarks}{tags}{parents}user:        {author}\ndate:        {date|date}\nsummary:     {desc|firstline}\n\n'
+changeset = 'changeset:   {rev}:{node|short}\n{branches}{bookmarks}{tags}phase:       {phase}\n{parents}user:        {author}\ndate:        {date|date}\nsummary:     {desc|firstline}\n\n'
 changeset_quiet = '{rev}:{node|short}\n'
 changeset_verbose = 'changeset:   {rev}:{node|short}\n{branches}{bookmarks}{tags}{parents}user:        {author}\ndate:        {date|date}\n{files}{file_copies_switch}description:\n{desc|strip}\n\n\n'
 changeset_debug = 'changeset:   {rev}:{node}\n{branches}{bookmarks}{tags}phase:       {phase}\n{parents}{manifest}user:        {author}\ndate:        {date|date}\n{file_mods}{file_adds}{file_dels}{file_copies_switch}{extras}description:\n{desc|strip}\n\n\n'

tests/test-log.t

@@ -88,9 +88,20 b' log on directory'
 
   $ hg log -f -l1 --style something
   abort: style 'something' not found
-  (available styles: changelog, bisect, default, xml, compact)
+  (available styles: changelog, bisect, default, xml, phases, compact)
   [255]
 
+-f, phases style
+
+
+  $ hg log -f -l1 --style phases
+  changeset:   4:7e4639b4691b
+  tag:         tip
+  phase:       draft
+  user:        test
+  date:        Thu Jan 01 00:00:05 1970 +0000
+  summary:     e
+  
 
 -f, but no args