mdiff/patch: fix bad hunk handling for unified diffs with zero context
Prior to this patch "hg diff -U0", i.e., zero lines of context, would
output hunk headers with a start line one greater than what GNU patch
and git output. Guido van Rossum documents the unified diff format[1]
as having a start line value "one lower than one would expect" for
zero length hunks.
Comparing the behaviour of the three systems prior to this patch in
transforming
c1
c3
to
c1
c2
c3
- GNU "diff -U0" reports the hunk as "@@ -1,0 +2 @@"
- "git diff -U0" reports the hunk as "@@ -1,0 +2 @@"
- "hg diff -U0" reports the hunk as "@@ -2,0 +2,1 @@"
After this patch, "hg diff -U0" reports "@@ -1,0 +2,1 @@".
Since "hg export --config diff.unified=0" outputs zero-context unified
diffs, "hg import" has also been updated to account for start lines
one less than expected for zero length hunk ranges.
[1]: http://www.artima.com/weblogs/viewpost.jsp?thread=164293
$ hg init repo
$ cd repo
$ cat > a <<EOF
> c
> c
> a
> a
> b
> a
> a
> c
> c
> EOF
$ hg ci -Am adda
adding a
$ cat > a <<EOF
> c
> c
> a
> a
> dd
> a
> a
> c
> c
> EOF
default context
$ hg diff --nodates
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -2,7 +2,7 @@
c
a
a
-b
+dd
a
a
c
invalid --unified
$ hg diff --nodates -U foo
abort: diff context lines count must be an integer, not 'foo'
[255]
$ hg diff --nodates -U 2
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -3,5 +3,5 @@
a
a
-b
+dd
a
a
$ hg --config diff.unified=2 diff --nodates
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -3,5 +3,5 @@
a
a
-b
+dd
a
a
$ hg diff --nodates -U 1
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -4,3 +4,3 @@
a
-b
+dd
a
invalid diff.unified
$ hg --config diff.unified=foo diff --nodates
abort: diff context lines count must be an integer, not 'foo'
[255]
0 lines of context hunk header matches gnu diff hunk header
$ hg init diffzero
$ cd diffzero
$ cat > f1 << EOF
> c2
> c4
> c5
> EOF
$ hg commit -Am0
adding f1
$ cat > f2 << EOF
> c1
> c2
> c3
> c4
> EOF
$ diff -U0 f1 f2
--- f1 * (glob)
+++ f2 * (glob)
@@ -0,0 +1 @@
+c1
@@ -1,0 +3 @@
+c3
@@ -3 +4,0 @@
-c5
[1]
$ mv f2 f1
$ hg diff -U0 --nodates
diff -r 55d8ff78db23 f1
--- a/f1
+++ b/f1
@@ -0,0 +1,1 @@
+c1
@@ -1,0 +3,1 @@
+c3
@@ -3,1 +4,0 @@
-c5
$ hg diff -U0 --nodates --git
diff --git a/f1 b/f1
--- a/f1
+++ b/f1
@@ -0,0 +1,1 @@
+c1
@@ -1,0 +3,1 @@
+c3
@@ -3,1 +4,0 @@
-c5
$ hg diff -U0 --nodates -p
diff -r 55d8ff78db23 f1
--- a/f1
+++ b/f1
@@ -0,0 +1,1 @@
+c1
@@ -1,0 +3,1 @@ c2
+c3
@@ -3,1 +4,0 @@ c4
-c5