[PATCH v3 0/2] Let merge-file write out conflict markers with correct EOLs

[Johannes Schindelin <johannes.schindelin@gmx.de>]

The original patch was sent by Beat Bolli in
http://thread.gmane.org/gmane.comp.version-control.git/281600

My suggestion to extend it to respect gitattributes led to
changes that broke the original patch. And they were misguided
to begin with (see below).

Since there have been a couple of "What's cooking" mails
containing unheard calls for updates on this patch, I took it
on myself to fix things.

Junio's comment that we might look at blobs containing CR/LF
line endings made me rethink the entire approach, and I am now
convinced that we need to abandon the entire idea to make the
conflict markers depend on config settings or attributes:
after all, I introduced `git merge-file` as a replacement for
GNU merge that can be used *outside* of any repository, by design.

The crucial idea hit me yesterday when I took a step back: all
we need to do is to ensure that the end-of-line style is matched
when *all* input files are LF-only, or when they are all CR/LF.
In all other cases, we have mixed line endings anyway.

And to do that, it is sufficient to look at *one single line
ending* in the context. Technically, it does not even have to be
the context, but the first line endings of the first file would
be enough, however it is so much more pleasant if the conflict
marker's eol matches the one of the preceding line.

To prevent my future self from repeating mistakes, I added a
little bit of background to the first commit message.

Triggered by a comment by Junio, I realized that a second patch is
needed: we need to make sure that the conflicting sections are also
augmented by the appropriate line endings if they lack any.

Relative to v2, the first patch changed only in the test code, to
accomodate for the newly-introduced second patch.


Johannes Schindelin (2):
  merge-file: let conflict markers match end-of-line style of the
    context
  merge-file: ensure that conflict sections match eol style

 t/t6023-merge-file.sh | 13 +++++++
 xdiff/xmerge.c        | 98 +++++++++++++++++++++++++++++++++++++++++----------
 2 files changed, 93 insertions(+), 18 deletions(-)

Interdiff vs v2:

 diff --git a/t/t6023-merge-file.sh b/t/t6023-merge-file.sh
 index f0cb9ce..1390548 100755
 --- a/t/t6023-merge-file.sh
 +++ b/t/t6023-merge-file.sh
 @@ -346,13 +346,14 @@ test_expect_success 'conflict at EOF without LF resolved by --union' \
  	 printf "line1\nline2\nline3x\nline3y" >expect.txt &&
  	 test_cmp expect.txt output.txt'
  
 -test_expect_success 'conflict markers match existing line endings' '
 -	append_cr <nolf-orig.txt >crlf-orig.txt &&
 -	append_cr <nolf-diff1.txt >crlf-diff1.txt &&
 -	append_cr <nolf-diff2.txt >crlf-diff2.txt &&
 +test_expect_success 'conflict sections match existing line endings' '
 +	printf "1\\r\\n2\\r\\n3" >crlf-orig.txt &&
 +	printf "1\\r\\n2\\r\\n4" >crlf-diff1.txt &&
 +	printf "1\\r\\n2\\r\\n5" >crlf-diff2.txt &&
  	test_must_fail git -c core.eol=crlf merge-file -p \
  		crlf-diff1.txt crlf-orig.txt crlf-diff2.txt >crlf.txt &&
  	test $(tr "\015" Q <crlf.txt | grep "\\.txtQ$" | wc -l) = 3 &&
 +	test $(tr "\015" Q <crlf.txt | grep "[345]Q$" | wc -l) = 3 &&
  	test_must_fail git -c core.eol=crlf merge-file -p \
  		nolf-diff1.txt nolf-orig.txt nolf-diff2.txt >nolf.txt &&
  	test $(tr "\015" Q <nolf.txt | grep "\\.txtQ$" | wc -l) = 0
 diff --git a/xdiff/xmerge.c b/xdiff/xmerge.c
 index c852acc..d98f430 100644
 --- a/xdiff/xmerge.c
 +++ b/xdiff/xmerge.c
 @@ -109,7 +109,7 @@ static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,
  	return 0;
  }
  
 -static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add_nl, char *dest)
 +static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
  {
  	xrecord_t **recs;
  	int size = 0;
 @@ -125,6 +125,12 @@ static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add
  	if (add_nl) {
  		i = recs[count - 1]->size;
  		if (i == 0 || recs[count - 1]->ptr[i - 1] != '\n') {
 +			if (needs_cr) {
 +				if (dest)
 +					dest[size] = '\r';
 +				size++;
 +			}
 +
  			if (dest)
  				dest[size] = '\n';
  			size++;
 @@ -133,14 +139,14 @@ static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add
  	return size;
  }
  
 -static int xdl_recs_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
 +static int xdl_recs_copy(xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
  {
 -	return xdl_recs_copy_0(0, xe, i, count, add_nl, dest);
 +	return xdl_recs_copy_0(0, xe, i, count, needs_cr, add_nl, dest);
  }
  
 -static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
 +static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int needs_cr, int add_nl, char *dest)
  {
 -	return xdl_recs_copy_0(1, xe, i, count, add_nl, dest);
 +	return xdl_recs_copy_0(1, xe, i, count, needs_cr, add_nl, dest);
  }
  
  /*
 @@ -172,15 +178,8 @@ static int is_eol_crlf(xdfile_t *file, int i)
  		file->recs[i - 1]->ptr[size - 2] == '\r';
  }
  
 -static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 -			      xdfenv_t *xe2, const char *name2,
 -			      const char *name3,
 -			      int size, int i, int style,
 -			      xdmerge_t *m, char *dest, int marker_size)
 +static int is_cr_needed(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m)
  {
 -	int marker1_size = (name1 ? strlen(name1) + 1 : 0);
 -	int marker2_size = (name2 ? strlen(name2) + 1 : 0);
 -	int marker3_size = (name3 ? strlen(name3) + 1 : 0);
  	int needs_cr;
  
  	/* Match post-images' preceding, or first, lines' end-of-line style */
 @@ -191,14 +190,25 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
  	if (needs_cr)
  		needs_cr = is_eol_crlf(&xe1->xdf1, 0);
  	/* If still undecided, use LF-only */
 -	if (needs_cr < 0)
 -		needs_cr = 0;
 +	return needs_cr < 0 ? 0 : needs_cr;
 +}
 +
 +static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
 +			      xdfenv_t *xe2, const char *name2,
 +			      const char *name3,
 +			      int size, int i, int style,
 +			      xdmerge_t *m, char *dest, int marker_size)
 +{
 +	int marker1_size = (name1 ? strlen(name1) + 1 : 0);
 +	int marker2_size = (name2 ? strlen(name2) + 1 : 0);
 +	int marker3_size = (name3 ? strlen(name3) + 1 : 0);
 +	int needs_cr = is_cr_needed(xe1, xe2, m);
  
  	if (marker_size <= 0)
  		marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
  
  	/* Before conflicting part */
 -	size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
 +	size += xdl_recs_copy(xe1, i, m->i1 - i, 0, 0,
  			      dest ? dest + size : NULL);
  
  	if (!dest) {
 @@ -217,7 +227,7 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
  	}
  
  	/* Postimage from side #1 */
 -	size += xdl_recs_copy(xe1, m->i1, m->chg1, 1,
 +	size += xdl_recs_copy(xe1, m->i1, m->chg1, needs_cr, 1,
  			      dest ? dest + size : NULL);
  
  	if (style == XDL_MERGE_DIFF3) {
 @@ -236,7 +246,7 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
  				dest[size++] = '\r';
  			dest[size++] = '\n';
  		}
 -		size += xdl_orig_copy(xe1, m->i0, m->chg0, 1,
 +		size += xdl_orig_copy(xe1, m->i0, m->chg0, needs_cr, 1,
  				      dest ? dest + size : NULL);
  	}
  
 @@ -251,7 +261,7 @@ static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
  	}
  
  	/* Postimage from side #2 */
 -	size += xdl_recs_copy(xe2, m->i2, m->chg2, 1,
 +	size += xdl_recs_copy(xe2, m->i2, m->chg2, needs_cr, 1,
  			      dest ? dest + size : NULL);
  	if (!dest) {
  		size += marker_size + 1 + needs_cr + marker2_size;
 @@ -290,21 +300,24 @@ static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
  						  marker_size);
  		else if (m->mode & 3) {
  			/* Before conflicting part */
 -			size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
 +			size += xdl_recs_copy(xe1, i, m->i1 - i, 0, 0,
  					      dest ? dest + size : NULL);
  			/* Postimage from side #1 */
 -			if (m->mode & 1)
 -				size += xdl_recs_copy(xe1, m->i1, m->chg1, (m->mode & 2),
 +			if (m->mode & 1) {
 +				int needs_cr = is_cr_needed(xe1, xe2, m);
 +
 +				size += xdl_recs_copy(xe1, m->i1, m->chg1, needs_cr, (m->mode & 2),
  						      dest ? dest + size : NULL);
 +			}
  			/* Postimage from side #2 */
  			if (m->mode & 2)
 -				size += xdl_recs_copy(xe2, m->i2, m->chg2, 0,
 +				size += xdl_recs_copy(xe2, m->i2, m->chg2, 0, 0,
  						      dest ? dest + size : NULL);
  		} else
  			continue;
  		i = m->i1 + m->chg1;
  	}
 -	size += xdl_recs_copy(xe1, i, xe1->xdf2.nrec - i, 0,
 +	size += xdl_recs_copy(xe1, i, xe1->xdf2.nrec - i, 0, 0,
  			      dest ? dest + size : NULL);
  	return size;
  }

-- 
2.7.0.windows.1.7.g55a05c8