tests/test-diff-color.t

patch: implement a new worddiff algorithm

The previous worddiff algorithm has many problems. The major problem is it
does a "similarity check" that selects a subset of matched lines to do
inline diffs. It is a bad idea because:

  - The "similarity check" is non-obvious to users. For example, a simple
    change from "long long x" to "int64_t x" will fail the similarity check
    and won't be diff-ed as expected.
  - Selecting "lines" to diff won't work as people expect if there are line
    wrapping changes.
  - It has a sad time complexity if lines do not match, could be O(N^2)-ish.

There are other problems in implementation details.

  - Lines can match across distant hunks (if the next hunk does not have
    "-" lines).
  - "difflib" is slow.

The solution would be removing the "similarity check", and just diff all
words in a same hunk. So no content will be missed and everything will be
diff-ed as expected. This is similar to what code review tool like
Phabricator does.

This diff implements the word diff algorithm as described above. It also
avoids difflib to be faster.

Note about colors: To be consistent, "changed inserted" parts and "purely
insertion blocks" should have a same color, since they do not exist in the
previous version. Instead of highlighting differences, this patch chooses to
dim common parts. This is also more consistent with Phabricator or GitHub
webpage. That said, the labels are defined in a way that people can still
highlight changed parts and leave purely inserted/deleted hunks use the
"non-highlighted" color.

As one example, running:

  hg log -pr df50b87d8f736aff8dc281f816bddcd6f306930c mercurial/commands.py \
    --config experimental.worddiff=1 --color=debug --config diff.unified=0

The previous algorithm outputs:

  [diff.file_a|--- a/mercurial/commands.py	Fri Mar 09 15:53:41 2018 +0100]
  [diff.file_b|+++ b/mercurial/commands.py	Sat Mar 10 12:33:19 2018 +0530]
  [diff.hunk|@@ -2039,1 +2039,4 @@]
  [diff.deleted|-][diff.deleted.highlight|@command('^forget',][diff.deleted| ][diff.deleted.highlight|walkopts,][diff.deleted| _('[OPTION]... FILE...'), inferrepo=True)]
  [diff.inserted|+@command(]
  [diff.inserted|+    '^forget',]
  [diff.inserted|+    walkopts + dryrunopts,]
  [diff.inserted|+ ][diff.inserted.highlight|  ][diff.inserted| _('[OPTION]... FILE...'), inferrepo=True)]
  [diff.hunk|@@ -2074,1 +2077,3 @@]
  [diff.deleted|-    rejected = cmdutil.forget(ui, repo, m, prefix="",][diff.deleted.highlight| explicitonly=False)[0]]
  [diff.inserted|+    dryrun = opts.get(r'dry_run')]
  [diff.inserted|+    rejected = cmdutil.forget(ui, repo, m, prefix="",]
  [diff.inserted|+                              explicitonly=False, dryrun=dryrun)[0]]

The new algorithm outputs:

  [diff.file_a|--- a/mercurial/commands.py	Fri Mar 09 15:53:41 2018 +0100]
  [diff.file_b|+++ b/mercurial/commands.py	Sat Mar 10 12:33:19 2018 +0530]
  [diff.hunk|@@ -2039,1 +2039,4 @@]
  [diff.deleted|-][diff.deleted.unchanged|@command(][diff.deleted.unchanged|'^forget',][diff.deleted.unchanged| ][diff.deleted.changed|walkopts][diff.deleted.unchanged|,][diff.deleted.changed| ][diff.deleted.unchanged|_('[OPTION]... FILE...'), inferrepo=True)]
  [diff.inserted|+][diff.inserted.unchanged|@command(]
  [diff.inserted|+][diff.inserted.changed|    ][diff.inserted.unchanged|'^forget',]
  [diff.inserted|+][diff.inserted.changed|    walkopts][diff.inserted.unchanged| ][diff.inserted.changed|+ dryrunopts][diff.inserted.unchanged|,]
  [diff.inserted|+][diff.inserted.changed|    ][diff.inserted.unchanged|_('[OPTION]... FILE...'), inferrepo=True)]
  [diff.hunk|@@ -2074,1 +2077,3 @@]
  [diff.deleted|-][diff.deleted.unchanged|    rejected = cmdutil.forget(ui, repo, m, prefix="",][diff.deleted.changed| ][diff.deleted.unchanged|explicitonly=False][diff.deleted.unchanged|)[0]]
  [diff.inserted|+][diff.inserted.changed|    dryrun = opts.get(r'dry_run')]
  [diff.inserted|+][diff.inserted.unchanged|    rejected = cmdutil.forget(ui, repo, m, prefix="",]
  [diff.inserted|+][diff.inserted.changed|                              ][diff.inserted.unchanged|explicitonly=False][diff.inserted.changed|, dryrun=dryrun][diff.inserted.unchanged|)[0]]

Practically, when diffing a 8k line change, the time spent on worddiff
reduces from 4 seconds to 0.14 seconds.

Differential Revision: https://phab.mercurial-scm.org/D3212

Setup

  $ cat <<EOF >> $HGRCPATH
  > [ui]
  > color = yes
  > formatted = always
  > paginate = never
  > [color]
  > mode = ansi
  > EOF
  $ hg init repo
  $ cd repo
  $ cat > a <<EOF
  > c
  > c
  > a
  > a
  > b
  > a
  > a
  > c
  > c
  > EOF
  $ hg ci -Am adda
  adding a
  $ cat > a <<EOF
  > c
  > c
  > a
  > a
  > dd
  > a
  > a
  > c
  > c
  > EOF

default context

  $ hg diff --nodates
  \x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
  \x1b[0;31;1m--- a/a\x1b[0m (esc)
  \x1b[0;32;1m+++ b/a\x1b[0m (esc)
  \x1b[0;35m@@ -2,7 +2,7 @@\x1b[0m (esc)
   c
   a
   a
  \x1b[0;31m-b\x1b[0m (esc)
  \x1b[0;32m+dd\x1b[0m (esc)
   a
   a
   c

(check that 'ui.color=yes' match '--color=auto')

  $ hg diff --nodates --config ui.formatted=no
  diff -r cf9f4ba66af2 a
  --- a/a
  +++ b/a
  @@ -2,7 +2,7 @@
   c
   a
   a
  -b
  +dd
   a
   a
   c

(check that 'ui.color=no' disable color)

  $ hg diff --nodates --config ui.formatted=yes --config ui.color=no
  diff -r cf9f4ba66af2 a
  --- a/a
  +++ b/a
  @@ -2,7 +2,7 @@
   c
   a
   a
  -b
  +dd
   a
   a
   c

(check that 'ui.color=always' force color)

  $ hg diff --nodates --config ui.formatted=no --config ui.color=always
  \x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
  \x1b[0;31;1m--- a/a\x1b[0m (esc)
  \x1b[0;32;1m+++ b/a\x1b[0m (esc)
  \x1b[0;35m@@ -2,7 +2,7 @@\x1b[0m (esc)
   c
   a
   a
  \x1b[0;31m-b\x1b[0m (esc)
  \x1b[0;32m+dd\x1b[0m (esc)
   a
   a
   c

--unified=2

  $ hg diff --nodates -U 2
  \x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
  \x1b[0;31;1m--- a/a\x1b[0m (esc)
  \x1b[0;32;1m+++ b/a\x1b[0m (esc)
  \x1b[0;35m@@ -3,5 +3,5 @@\x1b[0m (esc)
   a
   a
  \x1b[0;31m-b\x1b[0m (esc)
  \x1b[0;32m+dd\x1b[0m (esc)
   a
   a

diffstat

  $ hg diff --stat
   a |  2 \x1b[0;32m+\x1b[0m\x1b[0;31m-\x1b[0m (esc)
   1 files changed, 1 insertions(+), 1 deletions(-)
  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > record =
  > [ui]
  > interactive = true
  > [diff]
  > git = True
  > EOF

#if execbit

record

  $ chmod +x a
  $ hg record -m moda a <<EOF
  > y
  > y
  > EOF
  \x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
  \x1b[0;36;1mold mode 100644\x1b[0m (esc)
  \x1b[0;36;1mnew mode 100755\x1b[0m (esc)
  1 hunks, 1 lines changed
  \x1b[0;33mexamine changes to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
  
  \x1b[0;35m@@ -2,7 +2,7 @@ c\x1b[0m (esc)
   c
   a
   a
  \x1b[0;31m-b\x1b[0m (esc)
  \x1b[0;32m+dd\x1b[0m (esc)
   a
   a
   c
  \x1b[0;33mrecord this change to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
  

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH
  $ hg rollback
  repository tip rolled back to revision 0 (undo commit)
  working directory now based on revision 0

qrecord

  $ hg qrecord -m moda patch <<EOF
  > y
  > y
  > EOF
  \x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
  \x1b[0;36;1mold mode 100644\x1b[0m (esc)
  \x1b[0;36;1mnew mode 100755\x1b[0m (esc)
  1 hunks, 1 lines changed
  \x1b[0;33mexamine changes to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
  
  \x1b[0;35m@@ -2,7 +2,7 @@ c\x1b[0m (esc)
   c
   a
   a
  \x1b[0;31m-b\x1b[0m (esc)
  \x1b[0;32m+dd\x1b[0m (esc)
   a
   a
   c
  \x1b[0;33mrecord this change to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
  

  $ hg qpop -a
  popping patch
  patch queue now empty

#endif

issue3712: test colorization of subrepo diff

  $ hg init sub
  $ echo b > sub/b
  $ hg -R sub commit -Am 'create sub'
  adding b
  $ echo 'sub = sub' > .hgsub
  $ hg add .hgsub
  $ hg commit -m 'add subrepo sub'
  $ echo aa >> a
  $ echo bb >> sub/b

  $ hg diff -S
  \x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
  \x1b[0;31;1m--- a/a\x1b[0m (esc)
  \x1b[0;32;1m+++ b/a\x1b[0m (esc)
  \x1b[0;35m@@ -7,3 +7,4 @@\x1b[0m (esc)
   a
   c
   c
  \x1b[0;32m+aa\x1b[0m (esc)
  \x1b[0;1mdiff --git a/sub/b b/sub/b\x1b[0m (esc)
  \x1b[0;31;1m--- a/sub/b\x1b[0m (esc)
  \x1b[0;32;1m+++ b/sub/b\x1b[0m (esc)
  \x1b[0;35m@@ -1,1 +1,2 @@\x1b[0m (esc)
   b
  \x1b[0;32m+bb\x1b[0m (esc)

test tabs

  $ cat >> a <<EOF
  > 	one tab
  > 		two tabs
  > end tab	
  > mid	tab
  > 	all		tabs	
  > EOF
  $ hg diff --nodates
  \x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
  \x1b[0;31;1m--- a/a\x1b[0m (esc)
  \x1b[0;32;1m+++ b/a\x1b[0m (esc)
  \x1b[0;35m@@ -7,3 +7,9 @@\x1b[0m (esc)
   a
   c
   c
  \x1b[0;32m+aa\x1b[0m (esc)
  \x1b[0;32m+\x1b[0m	\x1b[0;32mone tab\x1b[0m (esc)
  \x1b[0;32m+\x1b[0m		\x1b[0;32mtwo tabs\x1b[0m (esc)
  \x1b[0;32m+end tab\x1b[0m\x1b[0;1;41m	\x1b[0m (esc)
  \x1b[0;32m+mid\x1b[0m	\x1b[0;32mtab\x1b[0m (esc)
  \x1b[0;32m+\x1b[0m	\x1b[0;32mall\x1b[0m		\x1b[0;32mtabs\x1b[0m\x1b[0;1;41m	\x1b[0m (esc)
  $ echo "[color]" >> $HGRCPATH
  $ echo "diff.tab = bold magenta" >> $HGRCPATH
  $ hg diff --nodates
  \x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
  \x1b[0;31;1m--- a/a\x1b[0m (esc)
  \x1b[0;32;1m+++ b/a\x1b[0m (esc)
  \x1b[0;35m@@ -7,3 +7,9 @@\x1b[0m (esc)
   a
   c
   c
  \x1b[0;32m+aa\x1b[0m (esc)
  \x1b[0;32m+\x1b[0m\x1b[0;1;35m	\x1b[0m\x1b[0;32mone tab\x1b[0m (esc)
  \x1b[0;32m+\x1b[0m\x1b[0;1;35m		\x1b[0m\x1b[0;32mtwo tabs\x1b[0m (esc)
  \x1b[0;32m+end tab\x1b[0m\x1b[0;1;41m	\x1b[0m (esc)
  \x1b[0;32m+mid\x1b[0m\x1b[0;1;35m	\x1b[0m\x1b[0;32mtab\x1b[0m (esc)
  \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 one with one tab
  > 		now with full two tabs
  > 	now tabs		everywhere, much fun
  > 
  > 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 one with two tab
  > 			now with full three tabs
  > 	now there are tabs		everywhere, much fun
  > 
  > 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|@@ -1,16 +1,17 @@]
  [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.deleted|-][diff.tab|	][diff.deleted|this one with one tab]
  [diff.deleted|-][diff.tab|		][diff.deleted|now with full two tabs]
  [diff.deleted|-][diff.tab|	][diff.deleted|now tabs][diff.tab|		][diff.deleted|everywhere, much fun]
  [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]
  [diff.inserted|+][diff.tab|	][diff.inserted|this one with two tab]
  [diff.inserted|+][diff.tab|			][diff.inserted|now with full three tabs]
  [diff.inserted|+][diff.tab|	][diff.inserted|now there are tabs][diff.tab|		][diff.inserted|everywhere, much fun]
   
   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|@@ -1,16 +1,17 @@]
  [diff.deleted|-][diff.deleted.changed|this][diff.deleted.unchanged| is the first ][diff.deleted.changed|line]
  [diff.deleted|-][diff.deleted.unchanged|this is the second line]
  [diff.deleted|-][diff.deleted.changed|    ][diff.deleted.unchanged|third line starts with space]
  [diff.deleted|-][diff.deleted.changed|+][diff.deleted.unchanged| starts with a ][diff.deleted.changed|plus][diff.deleted.unchanged| sign]
  [diff.deleted|-][diff.tab|	][diff.deleted.unchanged|this one with ][diff.deleted.changed|one][diff.deleted.unchanged| tab]
  [diff.deleted|-][diff.tab|		][diff.deleted.unchanged|now with full ][diff.deleted.changed|two][diff.deleted.unchanged| tabs]
  [diff.deleted|-][diff.tab|	][diff.deleted.unchanged|now ][diff.deleted.unchanged|tabs][diff.tab|		][diff.deleted.unchanged|everywhere, much fun]
  [diff.inserted|+][diff.inserted.changed|that][diff.inserted.unchanged| is the first ][diff.inserted.changed|paragraph]
  [diff.inserted|+][diff.inserted.changed|    ][diff.inserted.unchanged|this is the second line]
  [diff.inserted|+][diff.inserted.unchanged|third line starts with space]
  [diff.inserted|+][diff.inserted.changed|-][diff.inserted.unchanged| starts with a ][diff.inserted.changed|minus][diff.inserted.unchanged| sign]
  [diff.inserted|+][diff.tab|	][diff.inserted.unchanged|this one with ][diff.inserted.changed|two][diff.inserted.unchanged| tab]
  [diff.inserted|+][diff.tab|			][diff.inserted.unchanged|now with full ][diff.inserted.changed|three][diff.inserted.unchanged| tabs]
  [diff.inserted|+][diff.tab|	][diff.inserted.unchanged|now ][diff.inserted.changed|there are ][diff.inserted.unchanged|tabs][diff.tab|		][diff.inserted.unchanged|everywhere, much fun]
   
   this line won't change
   
   two lines are going to
  [diff.deleted|-][diff.deleted.unchanged|be changed into ][diff.deleted.changed|three][diff.deleted.unchanged|!]
  [diff.inserted|+][diff.inserted.changed|(entirely magically,]
  [diff.inserted|+][diff.inserted.changed| assuming this works)]
  [diff.inserted|+][diff.inserted.unchanged|be changed into ][diff.inserted.changed|four][diff.inserted.unchanged|!]
   
  [diff.deleted|-][diff.deleted.unchanged|three of those lines ][diff.deleted.changed|will]
  [diff.deleted|-][diff.deleted.changed|collapse][diff.deleted.unchanged| onto one]
  [diff.deleted|-][diff.deleted.changed|(to see if it works)]
  [diff.inserted|+][diff.inserted.unchanged|three of those lines ][diff.inserted.changed|have]
  [diff.inserted|+][diff.inserted.changed|collapsed][diff.inserted.unchanged| onto one]

multibyte character shouldn't be broken up in word diff:

  $ $PYTHON <<'EOF'
  > with open("utf8", "wb") as f:
  >     f.write(b"blah \xe3\x82\xa2 blah\n")
  > EOF
  $ hg ci -Am 'add utf8 char' utf8
  $ $PYTHON <<'EOF'
  > with open("utf8", "wb") as f:
  >     f.write(b"blah \xe3\x82\xa4 blah\n")
  > EOF
  $ hg ci -m 'slightly change utf8 char' utf8

  $ hg diff --config experimental.worddiff=True --color=debug -c.
  [diff.diffline|diff --git a/utf8 b/utf8]
  [diff.file_a|--- a/utf8]
  [diff.file_b|+++ b/utf8]
  [diff.hunk|@@ -1,1 +1,1 @@]
  [diff.deleted|-][diff.deleted.unchanged|blah ][diff.deleted.changed|\xe3\x82\xa2][diff.deleted.unchanged| blah] (esc)
  [diff.inserted|+][diff.inserted.unchanged|blah ][diff.inserted.changed|\xe3\x82\xa4][diff.inserted.unchanged| blah] (esc)