threads / patch / 23381

patchapply: Allow blank *trailing* context lines to match beyond EOF

Subject: [PATCH] apply: Allow blank *trailing* context lines to match beyond EOF

## tl;dr

2 messages between Apr 8, 2010 and Apr 8, 2010. Diffs are folded; open one to read it.

replies: 1people: 2as markdown or json

Björn Gustavsson· Apr 8, 2010, 04:14 UTC · lore

In 51667147be, "git apply --whitespace=fix" was extended to allow a blank context line to match beyond the end of the file, but only if the context line was in the leading part of the hunk (i.e. the hunk inserted additional contents at the end of the file).

Drop the restriction that the context line must be in the leading part of the hunk, thus allowing a file to be changed from:

 a
 (blank line)
to:
 b
 a
 (blank line)

Note that the blank line will be kept, because "--whitespace=fix" only removes trailing blank lines that a hunk would add, never trailing blank lines in the context.

Signed-off-by: Björn Gustavsson <bgustavsson@gmail.com>
---
This patch should fix the problem observed by Junio, but note that
there will be one or more blank lines left at the end of the
file.

I am not sure whether that should be fixed. In this particular case, the blank lines are part of the context but not part of the file being patched, so it could be argued that the blank lines should not be added back.

But there are already other circumstances in which "--whitespace=fix" does not guarantee that the file does not end with blank lines, for instance if we have:

 a
 b
 (blank line)
 (blank line)
 (blank line)
 (blank line)
 c
 d
and then delete the "c" and "d" lines:
 a
 b
 (blank line)
 (blank line)
 (blank line)
 (blank line)

In this case, not all of the blank lines are even part of the context, so even if we'll change the rules and remove blanks line in the context, there would still be blank lines left at the end of the file.

 builtin/apply.c          |   12 ++++++------
 t/t4124-apply-ws-rule.sh |   12 ++++++++++++
 2 files changed, 18 insertions(+), 6 deletions(-)
Show changes to 2 files +18 −6

builtin/apply.c, t/t4124-apply-ws-rule.sh

diff --git a/builtin/apply.c b/builtin/apply.c
index 7ca9047..d17e046 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -1864,13 +1864,13 @@ static int match_fragment(struct image *img,
 		if (match_end && (preimage->nr + try_lno != img->nr))
 			return 0;
 	} else if (ws_error_action == correct_ws_error &&
-		   (ws_rule & WS_BLANK_AT_EOF) && match_end) {
+		   (ws_rule & WS_BLANK_AT_EOF)) {
 		/*
-		 * This hunk that matches at the end extends beyond
-		 * the end of img, and we are removing blank lines
-		 * at the end of the file.  This many lines from the
-		 * beginning of the preimage must match with img, and
-		 * the remainder of the preimage must be blank.
+		 * This hunk extends beyond the end of img, and we are
+		 * removing blank lines at the end of the file.  This
+		 * many lines from the beginning of the preimage must
+		 * match with img, and the remainder of the preimage
+		 * must be blank.
 		 */
 		preimage_limit = img->nr - try_lno;
 	} else {
diff --git a/t/t4124-apply-ws-rule.sh b/t/t4124-apply-ws-rule.sh
index fb9ad24..451d75e 100755
--- a/t/t4124-apply-ws-rule.sh
+++ b/t/t4124-apply-ws-rule.sh
@@ -325,6 +325,18 @@ test_expect_success 'two missing blank lines at end with --whitespace=fix' '
 	test_cmp one expect
 '
 
+test_expect_success 'missing blank line at end, insert before end, --whitespace=fix' '
+	{ echo a; echo; } >one &&
+	git add one &&
+	{ echo b; echo a; echo; } >one &&
+	cp one expect &&
+	git diff -- one >patch &&
+	echo a >one &&
+	test_must_fail git apply patch &&
+	git apply --whitespace=fix patch &&
+	test_cmp one expect
+'
+
 test_expect_success 'shrink file with tons of missing blanks at end of file' '
 	{ echo a; echo b; echo c; } >one &&
 	cp one no-blank-lines &&
-- 
1.7.0.2.157.gb7e7f
Junio C Hamano· Apr 8, 2010, 05:32 UTC · re: Björn Gustavsson · lore

Re: [PATCH] apply: Allow blank *trailing* context lines to match beyond EOF

Björn Gustavsson <bgustavsson@gmail.com> writes:
Show 30 quoted lines
> This patch should fix the problem observed by Junio, but note that
> there will be one or more blank lines left at the end of the
> file.
>
> I am not sure whether that should be fixed. In this particular
> case, the blank lines are part of the context but not part of
> the file being patched, so it could be argued that the blank
> lines should not be added back.
>
> But there are already other circumstances in which
> "--whitespace=fix" does not guarantee that the file does
> not end with blank lines, for instance if we have:
>
>  a
>  b
>  (blank line)
>  (blank line)
>  (blank line)
>  (blank line)
>  c
>  d
>
> and then delete the "c" and "d" lines:
>
>  a
>  b
>  (blank line)
>  (blank line)
>  (blank line)
>  (blank line)

Even though I think these are both worth fixing, I do not think it should happen as part of this patch. Because the code that needs to "fix" the "extra blank bug" this patch introduces will need to deal with exactly the same horizon effect as your "deleting c and d at the end will not have the blank immediately after b in the context" example, I expect we will fix the fallout from this patch when we fix that "delete c and d at the end" example.

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