filemerge: use 'basic' as the default of '[ui] mergemarkers' for safety

Before this patch, 'detailed' is used as the default of '[ui]
mergemarkers'. This embeds non-ASCII characters in tags, branches,
bookmarks, author and/or commit descriptions into merged files in the
encoding specified by '--encoding' global option, 'HGENCODING' or
other locale setting environment variables.

But, if files to be merged use another encoding, this behavior breaks
consistency of encoding in merged files.

For example, ISO-2022-JP or EUC-JP are sometimes used as the file
encoding for Japanese characters, because of historical and/or
environmental reasons, even though UTF-8 or Shift-JIS are ordinarily
used as the terminal encoding.

This can't be resolved automatically, because Mercurial doesn't aware
encoding of managed files.

This patch uses 'basic' as the default of '[ui] mergemarkers' to avoid
embedding encoding sensitive characters for safety.

This patch puts '[ui] mergemarkers = detailed' into default hgrc file
for tests, to reduce changes for tests in this patch.

mercurial/filemerge.py

@@ -376,7 +376,7 b' def filemerge(repo, mynode, orig, fcd, f'
 
     ui.debug("my %s other %s ancestor %s\n" % (fcd, fco, fca))
 
-    markerstyle = ui.config('ui', 'mergemarkers', 'detailed')
+    markerstyle = ui.config('ui', 'mergemarkers', 'basic')
     if markerstyle == 'basic':
         formattedlabels = _defaultconflictlabels
     else:

mercurial/help/config.txt

@@ -1215,11 +1215,11 b' User interface controls.'
     For configuring merge tools see the ``[merge-tools]`` section.
 
 ``mergemarkers``
-    Sets the merge conflict marker label styling. The default ``detailed``
+    Sets the merge conflict marker label styling. The ``detailed``
     style uses the ``mergemarkertemplate`` setting to style the labels.
     The ``basic`` style just uses 'local' and 'other' as the marker label.
     One of ``basic`` or ``detailed``.
-    Default is ``detailed``.
+    Default is ``basic``.
 
 ``mergemarkertemplate``
     The template used to print the commit description next to each conflict
@@ -1227,6 +1227,13 b' User interface controls.'
     format.
     Defaults to showing the hash, tags, branches, bookmarks, author, and
     the first line of the commit description.
+    You have to pay attention to encodings of managed files, if you
+    use non-ASCII characters in tags, branches, bookmarks, author
+    and/or commit descriptions. At template expansion, non-ASCII
+    characters use the encoding specified by ``--encoding`` global
+    option, ``HGENCODING`` or other locale setting environment
+    variables. The difference of encoding between merged file and
+    conflict markers causes serious problem.
 
 ``portablefilenames``
     Check for portable filenames. Can be ``warn``, ``ignore`` or ``abort``.

tests/run-tests.py

@@ -648,6 +648,7 b' class Test(unittest.TestCase):'
         hgrc.write('[ui]\n')
         hgrc.write('slash = True\n')
         hgrc.write('interactive = False\n')
+        hgrc.write('mergemarkers = detailed\n')
         hgrc.write('[defaults]\n')
         hgrc.write('backout = -d "0 0"\n')
         hgrc.write('commit = -d "0 0"\n')

tests/test-basic.t

@@ -7,6 +7,7 b' Create a repository:'
   defaults.tag=-d "0 0"
   ui.slash=True
   ui.interactive=False
+  ui.mergemarkers=detailed
   $ hg init t
   $ cd t
 

tests/test-commandserver.py.out

@@ -80,6 +80,7 b' defaults.shelve=--date "0 0"'
 defaults.tag=-d "0 0"
 ui.slash=True
 ui.interactive=False
+ui.mergemarkers=detailed
 ui.foo=bar
 ui.nontty=true
  runcommand init foo
@@ -90,6 +91,7 b' defaults.shelve=--date "0 0"'
 defaults.tag=-d "0 0"
 ui.slash=True
 ui.interactive=False
+ui.mergemarkers=detailed
 ui.nontty=true
 
 testing hookoutput: