# bug in git diff --unified=0 ? 4 messages from 2009-05-02 to 2009-05-03. Participants: Shawn O. Pearce, Junio C Hamano. Thread: https://gitlist.dev/t/19161 ## Shawn O. Pearce, 2009-05-02 23:47 Subject: bug in git diff --unified=0 ? Message-ID: <20090502234701.GL23604@spearce.org> URL: https://gitlist.dev/e/20090502234701.GL23604%40spearce.org ``` I can't decide if this is a bug in JGit, or a bug in CGit, or just an area where the patch format is very unclear. The following 2 patches are identical, but use different context: git diff --unified=1: diff --git a/X b/X index a3648a1..2d44096 100644 --- a/X +++ b/X @@ -2,2 +2,3 @@ b +c d @@ -16,4 +17,2 @@ q -r -s t git diff --unified=0: diff --git a/X b/X index a3648a1..2d44096 100644 --- a/X +++ b/X @@ -2,0 +3 @@ +c @@ -17,2 +17,0 @@ -r -s Now lets look at JGit's output of that last patch, unified=0: diff --git a/X b/X index a3648a1..2d44096 100644 --- a/X +++ b/X @@ -3,0 +3,1 @@ +c @@ -17,2 +18,0 @@ -r -s Notice that `git diff --unified=1` said the first hunk started on line 2 of the pre-image, as the 2nd line of the file is the context line "b\n". I call that correct. However, `git diff --unified=0` said the first hunk started on line 2 of the pre-image, but there is no pre-image mentioned. JGit says it starts on line 3 of the pre-image, because the script is adding a "c\n" on line 3. The exact opposite behavior can be seen in the 2nd hunk, where we delete lines. Again, `git diff --unified=0` seems to behave as though we had 1 line of context, but we don't. -- Shawn. ``` ## Junio C Hamano, 2009-05-03 00:17 Subject: Re: bug in git diff --unified=0 ? Message-ID: <7vocub59b3.fsf@alter.siamese.dyndns.org> URL: https://gitlist.dev/e/7vocub59b3.fsf%40alter.siamese.dyndns.org In-Reply-To: <20090502234701.GL23604@spearce.org> ``` "Shawn O. Pearce" writes: > I can't decide if this is a bug in JGit, or a bug in CGit, or just > an area where the patch format is very unclear. > > The following 2 patches are identical, but use different context: > > git diff --unified=1: > > diff --git a/X b/X > index a3648a1..2d44096 100644 > --- a/X > +++ b/X > @@ -2,2 +2,3 @@ > b > +c > d > @@ -16,4 +17,2 @@ > q > -r > -s > t > > git diff --unified=0: > > diff --git a/X b/X > index a3648a1..2d44096 100644 > --- a/X > +++ b/X > @@ -2,0 +3 @@ > +c > @@ -17,2 +17,0 @@ > -r > -s > > Now lets look at JGit's output of that last patch, unified=0: > > diff --git a/X b/X > index a3648a1..2d44096 100644 > --- a/X > +++ b/X > @@ -3,0 +3,1 @@ > +c > @@ -17,2 +18,0 @@ > -r > -s I do not know what the current status of the POSIX draft for spliting "context diff" format into "copied context" and "unified context", but see http://www.opengroup.org/austin/aardvark/latest/xcubug2.txt for the definition that was on track the last time I checked. First the range of lines in each file shall be written in the following format: "@@^-%s^+%s^@@", , Each field shall be of the form: "%1d", if the range contains exactly one line, and: "%1d,%1d", , otherwise. If a range is empty, its beginning line number shall be the number of the line just before the range, or 0 if the empty range starts the file. So, JGit is wrong. ``` ## Shawn O. Pearce, 2009-05-03 00:23 Subject: Re: bug in git diff --unified=0 ? Message-ID: <20090503002352.GP23604@spearce.org> URL: https://gitlist.dev/e/20090503002352.GP23604%40spearce.org In-Reply-To: <7vocub59b3.fsf@alter.siamese.dyndns.org> ``` Junio C Hamano wrote: > I do not know what the current status of the POSIX draft for spliting > "context diff" format into "copied context" and "unified context", but > see http://www.opengroup.org/austin/aardvark/latest/xcubug2.txt for the > definition that was on track the last time I checked. Doh. Thank you for the clarification Junio. > So, JGit is wrong. Yup, I agree. /me works up a replacement patch. -- Shawn. ``` ## Junio C Hamano, 2009-05-03 05:18 Subject: Re: bug in git diff --unified=0 ? Message-ID: <7vy6ten4s0.fsf@alter.siamese.dyndns.org> URL: https://gitlist.dev/e/7vy6ten4s0.fsf%40alter.siamese.dyndns.org In-Reply-To: <7vocub59b3.fsf@alter.siamese.dyndns.org> ``` Junio C Hamano writes: > "Shawn O. Pearce" writes: > > I do not know what the current status of the POSIX draft for spliting > "context diff" format into "copied context" and "unified context"... POSIX 1003.1-2008 (base specifications issue 7) was published in December 2008. http://www.opengroup.org/onlinepubs/9699919799/toc.htm The text in the part I quoted in the previous message seems to be unchanged. http://www.opengroup.org/onlinepubs/9699919799/utilities/diff.html#tag_20_34_10_07 ```