patch: add within-line color diff capacity

The `diff' command usually writes deletion in red and insertions in green. This
patch adds within-line colors, to highlight which part of the lines differ.
Lines to compare are decided based on their similarity ratio, as computed by
difflib SequenceMatcher, with an arbitrary threshold (0.7) to decide at which
point two lines are considered entirely different (therefore no inline-diff
required).

The current implementation is kept behind an experimental flag in order to test
the effect on performance. In order to activate it, set inline-color-diff to
true in [experimental].

mercurial/cmdutil.py

@@ -1518,7 +1518,7 b' def diffordiffstat(ui, repo, diffopts, n'
         width = 80
         if not ui.plain():
             width = ui.termwidth()
-        chunks = patch.diff(repo, node1, node2, match, changes, diffopts,
+        chunks = patch.diff(repo, node1, node2, match, changes, opts=diffopts,
                             prefix=prefix, relroot=relroot,
                             hunksfilterfn=hunksfilterfn)
         for chunk, label in patch.diffstatui(util.iterlines(chunks),
@@ -1526,7 +1526,7 b' def diffordiffstat(ui, repo, diffopts, n'
             write(chunk, label=label)
     else:
         for chunk, label in patch.diffui(repo, node1, node2, match,
-                                         changes, diffopts, prefix=prefix,
+                                         changes, opts=diffopts, prefix=prefix,
                                          relroot=relroot,
                                          hunksfilterfn=hunksfilterfn):
             write(chunk, label=label)

mercurial/color.py

@@ -87,12 +87,14 b' except ImportError:'
     'branches.inactive': 'none',
     'diff.changed': 'white',
     'diff.deleted': 'red',
+    'diff.deleted.highlight': 'red bold underline',
     'diff.diffline': 'bold',
     'diff.extended': 'cyan bold',
     'diff.file_a': 'red bold',
     'diff.file_b': 'green bold',
     'diff.hunk': 'magenta',
     'diff.inserted': 'green',
+    'diff.inserted.highlight': 'green bold underline',
     'diff.tab': '',
     'diff.trailingwhitespace': 'bold red_background',
     'changeset.public': '',

mercurial/configitems.py

@@ -481,6 +481,9 b" coreconfigitem('experimental', 'evolutio"
 coreconfigitem('experimental', 'evolution.track-operation',
     default=True,
 )
+coreconfigitem('experimental', 'worddiff',
+    default=False,
+)
 coreconfigitem('experimental', 'maxdeltachainspan',
     default=-1,
 )

mercurial/mdiff.py

@@ -67,6 +67,7 b' class diffopts(object):'
         'ignoreblanklines': False,
         'upgrade': False,
         'showsimilarity': False,
+        'worddiff': False,
         }
 
     def __init__(self, **opts):

mercurial/patch.py

@@ -10,6 +10,7 b' from __future__ import absolute_import, '
 
 import collections
 import copy
+import difflib
 import email
 import errno
 import hashlib
@@ -2252,6 +2253,7 b' def difffeatureopts(ui, opts=None, untru'
         'showfunc': get('show_function', 'showfunc'),
         'context': get('unified', getter=ui.config),
     }
+    buildopts['worddiff'] = ui.configbool('experimental', 'worddiff')
 
     if git:
         buildopts['git'] = get('git')
@@ -2463,6 +2465,9 b' def diffhunks(repo, node1=None, node2=No'
 
 def difflabel(func, *args, **kw):
     '''yields 2-tuples of (output, label) based on the output of func()'''
+    inlinecolor = False
+    if kw.get('opts'):
+        inlinecolor = kw['opts'].worddiff
     headprefixes = [('diff', 'diff.diffline'),
                     ('copy', 'diff.extended'),
                     ('rename', 'diff.extended'),
@@ -2479,6 +2484,9 b' def difflabel(func, *args, **kw):'
     head = False
     for chunk in func(*args, **kw):
         lines = chunk.split('\n')
+        matches = {}
+        if inlinecolor:
+            matches = _findmatches(lines)
         for i, line in enumerate(lines):
             if i != 0:
                 yield ('\n', '')
@@ -2506,7 +2514,14 b' def difflabel(func, *args, **kw):'
                             if '\t' == token[0]:
                                 yield (token, 'diff.tab')
                             else:
-                                yield (token, label)
+                                if i in matches:
+                                    for l, t in _inlinediff(
+                                                  lines[i].rstrip(),
+                                                  lines[matches[i]].rstrip(),
+                                                  label):
+                                        yield (t, l)
+                                else:
+                                    yield (token, label)
                     else:
                         yield (stripline, label)
                     break
@@ -2515,6 +2530,70 b' def difflabel(func, *args, **kw):'
             if line != stripline:
                 yield (line[len(stripline):], 'diff.trailingwhitespace')
 
+def _findmatches(slist):
+    '''Look for insertion matches to deletion and returns a dict of
+    correspondences.
+    '''
+    lastmatch = 0
+    matches = {}
+    for i, line in enumerate(slist):
+        if line == '':
+            continue
+        if line[0] == '-':
+            lastmatch = max(lastmatch, i)
+            newgroup = False
+            for j, newline in enumerate(slist[lastmatch + 1:]):
+                if newline == '':
+                    continue
+                if newline[0] == '-' and newgroup: # too far, no match
+                    break
+                if newline[0] == '+': # potential match
+                    newgroup = True
+                    sim = difflib.SequenceMatcher(None, line, newline).ratio()
+                    if sim > 0.7:
+                        lastmatch = lastmatch + 1 + j
+                        matches[i] = lastmatch
+                        matches[lastmatch] = i
+                        break
+    return matches
+
+def _inlinediff(s1, s2, operation):
+    '''Perform string diff to highlight specific changes.'''
+    operation_skip = '+?' if operation == 'diff.deleted' else '-?'
+    if operation == 'diff.deleted':
+        s2, s1 = s1, s2
+
+    buff = []
+    # we never want to higlight the leading +-
+    if operation == 'diff.deleted' and s2.startswith('-'):
+        label = operation
+        token = '-'
+        s2 = s2[1:]
+        s1 = s1[1:]
+    elif operation == 'diff.inserted' and s1.startswith('+'):
+        label = operation
+        token = '+'
+        s2 = s2[1:]
+        s1 = s1[1:]
+
+    s = difflib.ndiff(re.split(br'(\W)', s2), re.split(br'(\W)', s1))
+    for part in s:
+        if part[0] in operation_skip:
+            continue
+        l = operation + '.highlight'
+        if part[0] in ' ':
+            l = operation
+        if l == label: # contiguous token with same label
+            token += part[2:]
+            continue
+        else:
+            buff.append((label, token))
+            label = l
+            token = part[2:]
+    buff.append((label, token))
+
+    return buff
+
 def diffui(*args, **kw):
     '''like diff(), but yields 2-tuples of (output, label) for ui.write()'''
     return difflabel(diff, *args, **kw)

tests/test-diff-color.t

@@ -259,3 +259,95 b' test tabs'
   \x1b[0;32m+\x1b[0m\x1b[0;1;35m	\x1b[0m\x1b[0;32mall\x1b[0m\x1b[0;1;35m		\x1b[0m\x1b[0;32mtabs\x1b[0m\x1b[0;1;41m	\x1b[0m (esc)
 
   $ cd ..
+
+test inline color diff
+
+  $ hg init inline
+  $ cd inline
+  $ cat > file1 << EOF
+  > this is the first line
+  > this is the second line
+  >     third line starts with space
+  > + starts with a plus sign
+  > 
+  > this line won't change
+  > 
+  > two lines are going to
+  > be changed into three!
+  > 
+  > three of those lines will
+  > collapse onto one
+  > (to see if it works)
+  > EOF
+  $ hg add file1
+  $ hg ci -m 'commit'
+  $ cat > file1 << EOF
+  > that is the first paragraph
+  >     this is the second line
+  > third line starts with space
+  > - starts with a minus sign
+  > 
+  > this line won't change
+  > 
+  > two lines are going to
+  > (entirely magically,
+  >  assuming this works)
+  > be changed into four!
+  > 
+  > three of those lines have
+  > collapsed onto one
+  > EOF
+  $ hg diff --config experimental.worddiff=False --color=debug
+  [diff.diffline|diff --git a/file1 b/file1]
+  [diff.file_a|--- a/file1]
+  [diff.file_b|+++ b/file1]
+  [diff.hunk|@@ -1,13 +1,14 @@]
+  [diff.deleted|-this is the first line]
+  [diff.deleted|-this is the second line]
+  [diff.deleted|-    third line starts with space]
+  [diff.deleted|-+ starts with a plus sign]
+  [diff.inserted|+that is the first paragraph]
+  [diff.inserted|+    this is the second line]
+  [diff.inserted|+third line starts with space]
+  [diff.inserted|+- starts with a minus sign]
+   
+   this line won't change
+   
+   two lines are going to
+  [diff.deleted|-be changed into three!]
+  [diff.inserted|+(entirely magically,]
+  [diff.inserted|+ assuming this works)]
+  [diff.inserted|+be changed into four!]
+   
+  [diff.deleted|-three of those lines will]
+  [diff.deleted|-collapse onto one]
+  [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
+  [diff.diffline|diff --git a/file1 b/file1]
+  [diff.file_a|--- a/file1]
+  [diff.file_b|+++ b/file1]
+  [diff.hunk|@@ -1,13 +1,14 @@]
+  [diff.deleted|-this is the ][diff.deleted.highlight|first][diff.deleted| line]
+  [diff.deleted|-this is the second line]
+  [diff.deleted|-][diff.deleted.highlight|    ][diff.deleted|third line starts with space]
+  [diff.deleted|-][diff.deleted.highlight|+][diff.deleted| starts with a ][diff.deleted.highlight|plus][diff.deleted| sign]
+  [diff.inserted|+that is the first paragraph]
+  [diff.inserted|+][diff.inserted.highlight|    ][diff.inserted|this is the ][diff.inserted.highlight|second][diff.inserted| line]
+  [diff.inserted|+third line starts with space]
+  [diff.inserted|+][diff.inserted.highlight|-][diff.inserted| starts with a ][diff.inserted.highlight|minus][diff.inserted| sign]
+   
+   this line won't change
+   
+   two lines are going to
+  [diff.deleted|-be changed into ][diff.deleted.highlight|three][diff.deleted|!]
+  [diff.inserted|+(entirely magically,]
+  [diff.inserted|+ assuming this works)]
+  [diff.inserted|+be changed into ][diff.inserted.highlight|four][diff.inserted|!]
+   
+  [diff.deleted|-three of those lines ][diff.deleted.highlight|will]
+  [diff.deleted|-][diff.deleted.highlight|collapse][diff.deleted| onto one]
+  [diff.deleted|-(to see if it works)]
+  [diff.inserted|+three of those lines ][diff.inserted.highlight|have]
+  [diff.inserted|+][diff.inserted.highlight|collapsed][diff.inserted| onto one]