diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Chris Moore]

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The diff-goto-source function doesn't work on context diff or unified diff
hunks when the context is set to 0 lines and when the hunk is only changing
a single line.

Example hunks which it fails on are this, generated using (let
((diff-switches "-c0")) (diff "/tmp/1" "/tmp/2")) :

diff -c0 /tmp/1 /tmp/2
*** /tmp/1      Sat Sep  8 15:44:04 2007
--- /tmp/2      Sat Sep  8 15:44:04 2007
***************
*** 4 ****
! one
--- 4 ----
! two

and this, generated using (let ((diff-switches "-u0")) (diff "/tmp/1"
"/tmp/2")) :

diff -u0 /tmp/1 /tmp/2
--- /tmp/1      2007-09-08 15:44:04.000000000 +0200
+++ /tmp/2      2007-09-08 15:44:04.000000000 +0200
@@ -4 +4 @@
-one
+two

I've fixed this bug.  The fix is to make parts of the regexps optional, and
to code what to do in the event that they're missing.

The patch is here: http://dooglus.rincevent.net/random/emacs-diff-patch.txt

I'll paste it here as well, in case you're reading this off-line.

I've signed papers with the FSF for my contributions to Emacs.

Chris.

-------

*** /home/chris/programs/emacs/lisp/diff-mode.el	Sat Sep  8 15:29:54 2007
--- /tmp/diff-mode.el	Sat Sep  8 15:40:53 2007
***************
*** 1217,1242 ****

         ;; A context diff.
         ((eq (char-after) ?*)
!         (if (not (looking-at "\\*\\{15\\}\\(?: .*\\)?\n\\*\\*\\*
\\([0-9]+\\),\\([0-9]+\\) \\*\\*\\*\\*"))
              (error "Unrecognized context diff first hunk header format")
            (forward-line 2)
            (diff-sanity-check-context-hunk-half
!            (1+ (- (string-to-number (match-string 2))
!                   (string-to-number (match-string 1)))))
!           (if (not (looking-at "--- \\([0-9]+\\),\\([0-9]+\\) ----$"))
                (error "Unrecognized context diff second hunk header format")
              (forward-line)
              (diff-sanity-check-context-hunk-half
!              (1+ (- (string-to-number (match-string 2))
!                     (string-to-number (match-string 1))))))))

         ;; A unified diff.
         ((eq (char-after) ?@)
          (if (not (looking-at
!                   "@@ -[0-9]+,\\([0-9]+\\) \\+[0-9]+,\\([0-9]+\\) @@"))
              (error "Unrecognized unified diff hunk header format")
!           (let ((before (string-to-number (match-string 1)))
!                 (after (string-to-number (match-string 2))))
              (forward-line)
              (while
                  (case (char-after)
--- 1217,1246 ----

         ;; A context diff.
         ((eq (char-after) ?*)
!         (if (not (looking-at "\\*\\{15\\}\\(?: .*\\)?\n\\*\\*\\*
\\([0-9]+\\)\\(?:,\\([0-9]+\\)\\)? \\*\\*\\*\\*"))
              (error "Unrecognized context diff first hunk header format")
            (forward-line 2)
            (diff-sanity-check-context-hunk-half
! 	   (if (match-string 2)
! 	       (1+ (- (string-to-number (match-string 2))
! 		      (string-to-number (match-string 1))))
! 	     1))
!           (if (not (looking-at "---
\\([0-9]+\\)\\(?:,\\([0-9]+\\)\\)? ----$"))
                (error "Unrecognized context diff second hunk header format")
              (forward-line)
              (diff-sanity-check-context-hunk-half
! 	     (if (match-string 2)
! 		 (1+ (- (string-to-number (match-string 2))
! 			(string-to-number (match-string 1))))
! 	       1)))))

         ;; A unified diff.
         ((eq (char-after) ?@)
          (if (not (looking-at
!                   "@@ -[0-9]+\\(?:,\\([0-9]+\\)\\)?
\\+[0-9]+\\(?:,\\([0-9]+\\)\\)? @@"))
              (error "Unrecognized unified diff hunk header format")
!           (let ((before (if (match-string 1) (string-to-number
(match-string 1)) 1))
!                 (after (if (match-string 2) (string-to-number
(match-string 2)) 1)))
              (forward-line)
              (while
                  (case (char-after)

-------

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Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Richard Stallman]

Your patch was mangled by your mailer.  Can you please send it uuencoded?
And can you please provide a change log entry?

It should be installed in Emacs 22.

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Chris Moore]

On 9/10/07, Richard Stallman <rms@gnu.org> wrote:
> Your patch was mangled by your mailer.  Can you please send it uuencoded?
> And can you please provide a change log entry?
>
> It should be installed in Emacs 22.
>

Sure.

Changelog:

2007-09-10  Chris Moore  <dooglus@gmail.com>

    * diff-mode.el: (diff-sanity-check-hunk): Fix to accept
    single-line hunks.

Patch:

begin 644 diff-mode-patch.txt.gz
M'XL("(`<Y48``V1I9F8M;6]D92UP871C:"YT>'0`U55-<YLP$#WC7[%A>I#`
M\B!2ZH0<3'Y#IZ>2`P%A-,:B%?*D']/_7H%Q;#X<0S/3-AI=M(_5KM[N/BS+
M@H2G*=D6"5NPW'!OX'ZW!M=QED"7OK?TKSVP'7TVZ()2=T8(:7LX-_"1?6D\
M/-]S_.O;QF-FM5=U!NK2Y9RZ[UVH30!Z-^ON#NXA+H1BWU0=9''$$&)?`<59
M)$F4*B8QK"P\NSKB/`4D"@4H+XH-%VL2*3##T`K#G]0+PU]AB%8^+/09KT)1
M`]4&;?_LD-L'6P/STP,\?Z.WB?$QEWU`)F4AP?PD)(N+M>`_6-)*'E(N2P79
M3FP@8U'")*2%W$;*;%^%M/4ID@G)N6#@=L":ZS(27'TG<<;B#6EBD.IBDD5Y
M>L)"Y4%M0`10J63%@BJ(V&T?=7"D0\<9V=MU'-SV.[A?\*.X6BW78>JK1CG/
MK4;)NSZI8V@MM5TDEWGM,-L#)S/[:F['LHMK7CISL1,\Y9J+RW,1G#YUJ#B#
MR9E!`&1?H.X8V$/F(!@Y$Z>)#U>MU4PYT[FB1Z91-HJO@=>@FHHQ=>H_X<6>
M><IXSGH]JX$X*EFK#+50'K3N0]WO_Y?6U=_,VQ:\>DNB9QRHZ!2U@>J;I@RL
MT7B-&M+G(/2/U/`,^V]&%HWC6P?8-Z82;TSC'`Z_H7^IDF<'R'X1_SNZV2L,
@Q6/ZNM?-S>6-G@Z4>TR)]S(]I0DGZ.QO@JG)$,,*````
`
end

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Richard Stallman]

Thanks.  If nobody installs it, please send a reminder every few days
until someone does.

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Thien-Thi Nguyen]

() "Chris Moore" <dooglus@gmail.com>
() Mon, 10 Sep 2007 13:20:23 +0200

   Changelog:
   Patch:

installed.

thi

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Stefan Monnier]

> () "Chris Moore" <dooglus@gmail.com>
> () Mon, 10 Sep 2007 13:20:23 +0200

>    Changelog:
>    Patch:

> installed.

Thanks.  But I still wonder: why would anybody use "-c0" or "-u0"?

If you don't want context, then you're better off with the plain or `ed'
diff formats, no?


        Stefan

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Glenn Morris]

Stefan Monnier wrote:

> Thanks.  But I still wonder: why would anybody use "-c0" or "-u0"?
>
> If you don't want context, then you're better off with the plain or `ed'
> diff formats, no?

Previously, it also failed to work when either of the files being
diffed was a single line file (so there was no context to display with
plain -c or -u).

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Stephen J. Turnbull]

Stefan Monnier writes:

 > Thanks.  But I still wonder: why would anybody use "-c0" or "-u0"?

For ChangeLogs, which rarely apply if they have any context.  The
unidiff format is preferred by XEmacs because it provides the headers
which identify the ChangeLog exactly.  I don't think it hurts that all
patches are in the same format.

Not a big deal, but since it's trivial to do, why not?

 > If you don't want context, then you're better off with the plain or `ed'
 > diff formats, no?

If you remember how to read them. :-)  I only ever see those in patch
.rej files.

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Stefan Monnier]

>> Thanks.  But I still wonder: why would anybody use "-c0" or "-u0"?
>> 
>> If you don't want context, then you're better off with the plain or `ed'
>> diff formats, no?

> Previously, it also failed to work when either of the files being
> diffed was a single line file (so there was no context to display with
> plain -c or -u).

Yes, the fix installed was right either way, I was just curious.


        Stefan

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Stefan Monnier]

>> Thanks.  But I still wonder: why would anybody use "-c0" or "-u0"?
> For ChangeLogs, which rarely apply if they have any context.

I guess that's an acceptable use for it.


        Stefan

Re: diff-mode doesn't like "-c0" or "-u0" diff output for single-line changes

[Thien-Thi Nguyen]

() Stefan Monnier <monnier@iro.umontreal.ca>
() Thu, 13 Sep 2007 13:42:15 -0400

   Thanks.  But I still wonder: why would anybody use "-c0" or "-u0"?

   If you don't want context, then you're better off with the plain or `ed'
   diff formats, no?

i use -u0 sometimes to save screen space, especially if the set of changes
consists mostly of small one-line edits (e.g., to a config file).  ymmv.

thi