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xdl_merge(): make XDL_MERGE_ZEALOUS output simpler

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When a merge conflicts, there are often less than three common lines
between two conflicting regions.

Since a conflict takes up as many lines as are conflicting, plus three
lines for the commit markers,  the output will be shorter (and thus,
simpler) in this case, if the common lines will be merged into the
conflicting regions.

This patch merges up to three common lines into the conflicts.

For example, what looked like this before this patch:

	<<<<<<<
	if (a == 1)
	=======
	if (a != 0)
	>>>>>>>
	{
		int i;
	<<<<<<<
		a = 0;
	=======
		a = !a;
	>>>>>>>

will now look like this:

	<<<<<<<
	if (a == 1)
	{
		int i;
		a = 0;
	=======
	if (a != 0)
	{
		int i;
		a = !a;
	>>>>>>>

Suggested Linus (based on ideas by "Voltage Spike" -- if that name is
real, it is mighty cool).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin 2008-02-17 19:07:19 +00:00 committed by Junio C Hamano
parent cf5c51efc9
commit f407f14dea
2 changed files with 56 additions and 1 deletions
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10
t/t6023-merge-file.sh
View file

@ -139,4 +139,14 @@ test_expect_success 'binary files cannot be merged' '
grep "Cannot merge binary files" merge.err
'
sed -e "s/deerit.$/deerit;/" -e "s/me;$/me./" < new5.txt > new6.txt
sed -e "s/deerit.$/deerit,/" -e "s/me;$/me,/" < new5.txt > new7.txt
test_expect_success 'MERGE_ZEALOUS simplifies non-conflicts' '
! git merge-file -p new6.txt new5.txt new7.txt > output &&
test 1 = $(grep ======= < output | wc -l)
'
test_done

47
xdiff/xmerge.c
View file

@ -248,6 +248,49 @@ static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
return 0;
}
/*
* This function merges m and m->next, marking everything between those hunks
* as conflicting, too.
*/
static void xdl_merge_two_conflicts(xdmerge_t *m)
{
xdmerge_t *next_m = m->next;
m->chg1 = next_m->i1 + next_m->chg1 - m->i1;
m->chg2 = next_m->i2 + next_m->chg2 - m->i2;
m->next = next_m->next;
free(next_m);
}
/*
* If there are less than 3 non-conflicting lines between conflicts,
* it appears simpler -- because it takes up less (or as many) lines --
* if the lines are moved into the conflicts.
*/
static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m)
{
int result = 0;
if (!m)
return result;
for (;;) {
xdmerge_t *next_m = m->next;
int begin, end;
if (!next_m)
return result;
begin = m->i1 + m->chg1;
end = next_m->i1;
if (m->mode != 0 || next_m->mode != 0 || end - begin > 3)
m = next_m;
else {
result++;
xdl_merge_two_conflicts(m);
}
}
}
/*
* level == 0: mark all overlapping changes as conflict
* level == 1: mark overlapping changes as conflict only if not identical
@ -355,7 +398,9 @@ static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1, const char *name1,
if (!changes)
changes = c;
/* refine conflicts */
if (level > 1 && xdl_refine_conflicts(xe1, xe2, changes, xpp) < 0) {
if (level > 1 &&
(xdl_refine_conflicts(xe1, xe2, changes, xpp) < 0 ||
xdl_simplify_non_conflicts(xe1, changes) < 0)) {
xdl_cleanup_merge(changes);
return -1;
}