comparison mercurial/patch.py @ 32979:66117dae87f9

patch: rewrite reversehunks (issue5337)

The old reversehunks code accesses "crecord.uihunk._hunk", which is the raw
recordhunk without crecord selection information, therefore "revert -i"
cannot revert individual lines, aka. issue5337.

The patch rewrites related logic to return the right reverse hunk for
revert. Namely,

 1. "fromline" and "toline" are correctly swapped [1]
 2. crecord.uihunk generates a correct reverse hunk [2]

Besides, reversehunks(hunks) will no longer modify its input "hunks", which
is more expected.

[1]: To explain why "fromline" and "toline" need to be swapped, take the
     following example:

  $ cat > a <<EOF
  > 1
  > 2
  > 3
  > 4
  > EOF

  $ cat > b <<EOF
  > 2
  > 3
  > 5
  > EOF

  $ diff a b
  1d0   <---- "1" is "fromline" and "0" is "toline"
  < 1         and they are swapped if diff from the reversed direction
  4c3             |
  < 4             |
  ---             |
  > 5             |
                  |
  $ diff b a      |
  0a1   <---------+
  > 1
  3c4   <---- also "4c3" gets swapped to "3c4"
  < 5
  ---
  > 4

[2]: This is a bit tricky.

For example, given a file which is empty in working parent but has 3 lines
in working copy, and the user selection:

    select hunk to discard
    [x] +1
    [ ] +2
    [x] +3

The user intent is to drop "1" and "3" in working copy but keep "2", so the
reverse patch would be something like:

        -1
         2 (2 is a "context line")
        -3

We cannot just take all selected lines and swap "-" and "+", which will be:

        -1
        -3

That patch won't apply because of "2". So the correct way is to insert "2"
as a "context line" by inserting it first then deleting it:

        -2
        +2

Therefore, the correct revert patch is:

        -1
        -2
        +2
        -3

It could be reordered to look more like a common diff hunk:

        -1
        -2
        -3
        +2

Note: It's possible to return multiple hunks so there won't be lines like
"-2", "+2". But the current implementation is much simpler.

For deletions, like the working parent has "1\n2\n3\n" and it was changed to
empty in working copy:

    select hunk to discard
    [x] -1
    [ ] -2
    [x] -3

The user intent is to drop the deletion of 1 and 3 (in other words, keep
those lines), but still delete "2".

The reverse patch is meant to be applied to working copy which is empty.
So the patch would be:

        +1
        +3

That is to say, there is no need to special handle the unselected "2" like
the above insertion case.

32978:41b081ac2145

    def countchanges(self, hunk):
        """hunk -> (n+,n-)"""
        add = len([h for h in hunk if h[0] == '+'])
        rem = len([h for h in hunk if h[0] == '-'])
        return add, rem

    def write(self, fp):
        delta = len(self.before) + len(self.after)
        if self.after and self.after[-1] == '\\ No newline at end of file\n':
            delta -= 1

    @@ -1,4 +1,3 @@
    -firstline
     c
     1
     2
    @@ -1,6 +2,6 @@
     c
     1
     2
    - 3
    +4
     5
     d
    @@ -5,3 +6,2 @@
     5
     d
    -lastline

    '''

    from . import crecord as crecordmod
    newhunks = []
    for c in hunks:
        if isinstance(c, crecordmod.uihunk):
            # curses hunks encapsulate the record hunk in _hunk
            c = c._hunk
        if isinstance(c, recordhunk):
            for j, line in enumerate(c.hunk):
                if line.startswith("-"):
                    c.hunk[j] = "+" + c.hunk[j][1:]
                elif line.startswith("+"):
                    c.hunk[j] = "-" + c.hunk[j][1:]
            c.added, c.removed = c.removed, c.added
        newhunks.append(c)
    return newhunks

def parsepatch(originalchunks):
    """patch -> [] of headers -> [] of hunks """

32979:66117dae87f9

    def countchanges(self, hunk):
        """hunk -> (n+,n-)"""
        add = len([h for h in hunk if h[0] == '+'])
        rem = len([h for h in hunk if h[0] == '-'])
        return add, rem

    def reversehunk(self):
        """return another recordhunk which is the reverse of the hunk

        If this hunk is diff(A, B), the returned hunk is diff(B, A). To do
        that, swap fromline/toline and +/- signs while keep other things
        unchanged.
        """
        m = {'+': '-', '-': '+'}
        hunk = ['%s%s' % (m[l[0]], l[1:]) for l in self.hunk]
        return recordhunk(self.header, self.toline, self.fromline, self.proc,
                          self.before, hunk, self.after)

    def write(self, fp):
        delta = len(self.before) + len(self.after)
        if self.after and self.after[-1] == '\\ No newline at end of file\n':
            delta -= 1

    @@ -1,4 +1,3 @@
    -firstline
     c
     1
     2
    @@ -2,6 +1,6 @@
     c
     1
     2
    - 3
    +4
     5
     d
    @@ -6,3 +5,2 @@
     5
     d
    -lastline

    '''

    newhunks = []
    for c in hunks:
        if util.safehasattr(c, 'reversehunk'):
            c = c.reversehunk()
        newhunks.append(c)
    return newhunks

def parsepatch(originalchunks):
    """patch -> [] of headers -> [] of hunks """