diff: graduate word-diff option from experimental

Per 4.6 Sprint notes.

I've also made it gated by "formatchanging" since it could change the output
if we had an option to highlight words without using colors.

mercurial/configitems.py

@@ -147,6 +147,9 b" coreconfigitem('annotate', 'nobinary',"
 coreconfigitem('annotate', 'noprefix',
     default=False,
 )
+coreconfigitem('annotate', 'word-diff',
+    default=False,
+)
 coreconfigitem('auth', 'cookiefile',
     default=None,
 )
@@ -399,6 +402,9 b" coreconfigitem('diff', 'nobinary',"
 coreconfigitem('diff', 'noprefix',
     default=False,
 )
+coreconfigitem('diff', 'word-diff',
+    default=False,
+)
 coreconfigitem('email', 'bcc',
     default=None,
 )
@@ -512,9 +518,6 b" coreconfigitem('experimental', 'evolutio"
 coreconfigitem('experimental', 'evolution.track-operation',
     default=True,
 )
-coreconfigitem('experimental', 'worddiff',
-    default=False,
-)
 coreconfigitem('experimental', 'maxdeltachainspan',
     default=-1,
 )

mercurial/diffutil.py

@@ -53,7 +53,6 b' def difffeatureopts(ui, opts=None, untru'
         'showfunc': get('show_function', 'showfunc'),
         'context': get('unified', getter=ui.config),
     }
-    buildopts['worddiff'] = ui.configbool('experimental', 'worddiff')
     buildopts['xdiff'] = ui.configbool('experimental', 'xdiff')
 
     if git:
@@ -101,5 +100,6 b' def difffeatureopts(ui, opts=None, untru'
         buildopts['nobinary'] = (not binary if binary is not None
                                  else get('nobinary', forceplain=False))
         buildopts['noprefix'] = get('noprefix', forceplain=False)
+        buildopts['worddiff'] = get('word_diff', 'word-diff', forceplain=False)
 
     return mdiff.diffopts(**pycompat.strkwargs(buildopts))

mercurial/help/config.txt

@@ -702,6 +702,9 b' for related options for the annotate com'
 ``unified``
     Number of lines of context to show.
 
+``word-diff``
+    Highlight changed words.
+
 ``email``
 ---------
 

tests/test-diff-color.t

@@ -304,7 +304,7 b' test inline color diff'
   > three of those lines have
   > collapsed onto one
   > EOF
-  $ hg diff --config experimental.worddiff=False --color=debug
+  $ hg diff --config diff.word-diff=False --color=debug
   [diff.diffline|diff --git a/file1 b/file1]
   [diff.file_a|--- a/file1]
   [diff.file_b|+++ b/file1]
@@ -337,7 +337,7 b' test inline color diff'
   [diff.deleted|-(to see if it works)]
   [diff.inserted|+three of those lines have]
   [diff.inserted|+collapsed onto one]
-  $ hg diff --config experimental.worddiff=True --color=debug
+  $ hg diff --config diff.word-diff=True --color=debug
   [diff.diffline|diff --git a/file1 b/file1]
   [diff.file_a|--- a/file1]
   [diff.file_b|+++ b/file1]
@@ -384,7 +384,7 b" multibyte character shouldn't be broken "
   > EOF
   $ hg ci -m 'slightly change utf8 char' utf8
 
-  $ hg diff --config experimental.worddiff=True --color=debug -c.
+  $ hg diff --config diff.word-diff=True --color=debug -c.
   [diff.diffline|diff --git a/utf8 b/utf8]
   [diff.file_a|--- a/utf8]
   [diff.file_b|+++ b/utf8]