threads / patch / 28946

patchapply: squash consecutive slashes with p_value > 0

Subject: [PATCH] apply: squash consecutive slashes with p_value > 0

## tl;dr

5 messages between Nov 16, 2011 and Nov 17, 2011. Diffs are folded; open one to read it.

replies: 4people: 2as markdown or json

Robie Basak· Nov 16, 2011, 12:04 UTC · lore

"patch" works with -p1 and diffs in the following form:
    --- foo.orig//bar
    +++ foo//bar
    ...

patch(1) says that "A sequence of one or more adjacent slashes is counted as a single slash."

This patch amends git-apply's filename parsing to behave in the same way, eliminating both '/'s with -p1 in this example.

Test case included.

Signed-off-by: Robie Basak <robie.basak@canonical.com>
---
 builtin/apply.c              |    8 ++++++--
 t/t4153-apply-doubleslash.sh |   29 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100755 t/t4153-apply-doubleslash.sh

Show changes to 2 files +34 −2

builtin/apply.c, t/t4153-apply-doubleslash.sh

diff --git a/builtin/apply.c b/builtin/apply.c
index 84a8a0b..78e25fa 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -627,9 +627,13 @@ static char *find_name_common(const char *line, char *def, int p_value,
 			if (name_terminate(start, line-start, c, terminate))
 				break;
 		}
-		line++;
-		if (c == '/' && !--p_value)
+		if (c == '/' && !--p_value) {
+			while (*line == '/')
+			    line++;
 			start = line;
+		} else {
+			line++;
+		}
 	}
 	if (!start)
 		return squash_slash(def);
diff --git a/t/t4153-apply-doubleslash.sh b/t/t4153-apply-doubleslash.sh
new file mode 100755
index 0000000..1ea76b5
--- /dev/null
+++ b/t/t4153-apply-doubleslash.sh
@@ -0,0 +1,29 @@
+#!/bin/sh
+#
+# Copyright (c) 2011 Canonical Ltd.
+#
+
+test_description='git apply filenames with double slashes
+
+Try to apply a patch with git-apply where the filename specified has a double
+slash after the first (to-be-stripped) component'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_commit 1 f &&
+	cat > good.patch <<EOF
+diff -u a//f b//f
+--- a//f
++++ b//f
+@@ -1 +1 @@
+-1
++2
+EOF
+'
+
+test_expect_success 'apply diff with double slashes in filenames' '
+	git apply good.patch 2>err
+'
+
+test_done

-- 
1.7.5.4

Junio C Hamano· Nov 16, 2011, 17:36 UTC · re: Robie Basak · lore

Re: [PATCH] apply: squash consecutive slashes with p_value > 0

Robie Basak <robie.basak@canonical.com> writes:

Show 7 quoted lines

> "patch" works with -p1 and diffs in the following form:
>     --- foo.orig//bar
>     +++ foo//bar
>     ...
>
> patch(1) says that "A sequence of one or more adjacent slashes is
> counted as a single slash."

It merely says patch(1) treats duplicate slashes that way; it does not mean it is a useful thing to do in the real life.

Could you justify why such a change is a good thing in your proposed commit log message?

>  builtin/apply.c              |    8 ++++++--
>  t/t4153-apply-doubleslash.sh |   29 +++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+), 2 deletions(-)
>  create mode 100755 t/t4153-apply-doubleslash.sh

Can we avoid wasting a new test number for just a single trivial test by findign appropriate places in existing tests to add new ones to? I think 4133 may be one of the good places (not just checkint between a/f vs b/f, you would check a//f vs b/f and somesuch).

Show 14 quoted lines

> diff --git a/builtin/apply.c b/builtin/apply.c
> index 84a8a0b..78e25fa 100644
> --- a/builtin/apply.c
> +++ b/builtin/apply.c
> @@ -627,9 +627,13 @@ static char *find_name_common(const char *line, char *def, int p_value,
>  			if (name_terminate(start, line-start, c, terminate))
>  				break;
>  		}
> -		line++;
> -		if (c == '/' && !--p_value)
> +		if (c == '/' && !--p_value) {
> +			while (*line == '/')
> +			    line++;
>  			start = line;

I am not sure if this is sufficient or necessarily correct.

You are de-dupling slashes only when p_value hits 0. When working on an input "a///b//c" with -p3, your loop strips one slash per decrement of p_value between "a" and "b" and then you notice slashes after "b" are duplicated and clean them up, which would mean you normalized the input to "a///b/c", not "a/b/c", no?

Robie Basak· Nov 17, 2011, 17:55 UTC · lore

Re: [PATCH] apply: squash consecutive slashes with p_value > 0

On Thu, Nov 17, 2011 at 09:43:02AM -0800, Junio C Hamano wrote:

> I didn't mention this, but I suspect the code with your patch would not
> touch redundant slashes after it finds "start", either.

What is happening to me is that b//foo with -p1 gets split at the first slash and then git apply cannot find /foo when it should be looking for foo. But in the case of b/foo//bar and -p1, without squashing extra slashes it would look for foo//bar which I presume that it would still be able to find.

So in my case, I only need duplicate slashes around the -p boundary point to be removed. I assumed that the squash_slash() later on would eliminate the rest, but I didn't look into this; if it does it'd be a different issue to the one that I'm seeing.

I'm now confused about what it will do (which is why I need to look at it again to make sure), but if it turns out to be easier to just handle that one boundary point, would you accept a patch that eliminates just that duplicate, on the basis that in Unix-land duplicate slashes are perfectly acceptable to be left lying around?

Thanks,

Robie

Junio C Hamano· Nov 17, 2011, 18:07 UTC · re: Robie Basak · lore

Re: [PATCH] apply: squash consecutive slashes with p_value > 0

Robie Basak <robie.basak@canonical.com> writes:

Show 5 quoted lines

> I'm now confused about what it will do (which is why I need to look at
> it again to make sure), but if it turns out to be easier to just handle
> that one boundary point, would you accept a patch that eliminates just
> that duplicate, on the basis that in Unix-land duplicate slashes are
> perfectly acceptable to be left lying around?

If that is the case, I would rather say we should even shoot for simpler. Just tell the patch generator not to include unneeded double slashes.

Robie Basak· Nov 17, 2011, 18:57 UTC · re: Junio C Hamano · lore

Re: [PATCH] apply: squash consecutive slashes with p_value > 0

On Thu, Nov 17, 2011 at 10:07:27AM -0800, Junio C Hamano wrote:

> If that is the case, I would rather say we should even shoot for
> simpler. Just tell the patch generator not to include unneeded double
> slashes.

I don't have a choice about the patch generator. These are humans typing "diff -ur foo.orig/ foo/" which I think is reasonable.

IMHO, this is a bug in git-apply's -p behaviour. It's not so much about stripping double slashes; more about doing the -p split in the middle of the doubled slashes rather than the end. patch does the right thing.