[PATCH] git-subtree: Avoid using echo -n even indirectly

[PATCH] git-subtree: Avoid using echo -n even indirectly

[Paolo G. Giarrusso]

Since say uses echo, this uses echo -n, which is not portable - see
19c3c5fdcb35b66b792534c5dc4e8d87a3952d2a.

Without this commit, the output looks like:

...
-n 1891/    1936 (1883)
-n 1892/    1936 (1884)
-n 1893/    1936 (1885)
...

Signed-off-by: Paolo G. Giarrusso <p.giarrusso@gmail.com>
---

Please CC me on replies, as I am not subscribed to this mailing list.
I am tracking this submission via https://github.com/git/git/pull/61, which I'll
duly close myself when the discussion is resolved.

 contrib/subtree/git-subtree.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index 7d7af03..ebfb78f 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -592,7 +592,9 @@ cmd_split()
 	eval "$grl" |
 	while read rev parents; do
 		revcount=$(($revcount + 1))
-		say -n "$revcount/$revmax ($createcount)
"
+		if [ -z "$quiet" ]; then
+			printf "%s" "$revcount/$revmax ($createcount)
" >&2
+		fi
 		debug "Processing commit: $rev"
 		exists=$(cache_get $rev)
 		if [ -n "$exists" ]; then
-- 
1.8.4

Re: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Tay Ray Chuan]

On Wed, Oct 9, 2013 at 11:57 AM, Paolo G. Giarrusso
<p.giarrusso@gmail.com> wrote:
> diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
> index 7d7af03..ebfb78f 100755
> --- a/contrib/subtree/git-subtree.sh
> +++ b/contrib/subtree/git-subtree.sh
> @@ -592,7 +592,9 @@ cmd_split()
>         eval "$grl" |
>         while read rev parents; do
>                 revcount=$(($revcount + 1))
> -               say -n "$revcount/$revmax ($createcount)
> "
> +               if [ -z "$quiet" ]; then
> +                       printf "%s" "$revcount/$revmax ($createcount)
> " >&2
> +               fi

Reviewers might wish to know that "say" in git-subtree is defined as

        say()
        {
                if [ -z "$quiet" ]; then
                        echo "$@" >&2
               fi
        }

Hence the "if" and the redirect.

-- 
Cheers,
Ray Chuan

Fwd: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Paolo Giarrusso]

(Resending without HTML).

On Wed, Oct 9, 2013 at 12:20 PM, Tay Ray Chuan <rctay89@gmail.com> wrote:
>
> On Wed, Oct 9, 2013 at 11:57 AM, Paolo G. Giarrusso
> <p.giarrusso@gmail.com> wrote:
> > diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
> > index 7d7af03..ebfb78f 100755
> > --- a/contrib/subtree/git-subtree.sh
> > +++ b/contrib/subtree/git-subtree.sh
> > @@ -592,7 +592,9 @@ cmd_split()
> >         eval "$grl" |
> >         while read rev parents; do
> >                 revcount=$(($revcount + 1))
> > -               say -n "$revcount/$revmax ($createcount)
> > "
> > +               if [ -z "$quiet" ]; then
> > +                       printf "%s" "$revcount/$revmax ($createcount)
> > " >&2

An additional note for reviewers and appliers: the original and the
patched codeboth embed a literal ^M, not a new line, go to back to the
beginning of the line and overwrite it, so the above is not a
consequence of line-wrap.

I used git-format-patch and git-send-email, and the ^M is visible in
Vim in the exported patch (that's why I didn't remark on it).
Seeing the email, I wonder whether there's hope something like that
can be preserved in an email, and whether the code should use some
escape sequence instead.

> > +               fi
>
> Reviewers might wish to know that "say" in git-subtree is defined as
>
>         say()
>         {
>                 if [ -z "$quiet" ]; then
>                         echo "$@" >&2
>                fi
>         }
>
> Hence the "if" and the redirect.

Indeed. I considered having a variant of `say` instead of inlining and
customizing it, but for once I decided to keep this simple, since this
variant of `say` is currently used only once. Otherwise, one could
change say to use printf, but that's more invasive.

Cheers,
-- 
Paolo G. Giarrusso - Ph.D. Student, Philipps-University Marburg
http://www.informatik.uni-marburg.de/~pgiarrusso/

Re: Fwd: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Johannes Sixt]

Am 10/9/2013 12:32, schrieb Paolo Giarrusso:
> On Wed, Oct 9, 2013 at 12:20 PM, Tay Ray Chuan <rctay89@gmail.com> wrote:
>> On Wed, Oct 9, 2013 at 11:57 AM, Paolo G. Giarrusso
>> <p.giarrusso@gmail.com> wrote:
>>> diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
>>> index 7d7af03..ebfb78f 100755
>>> --- a/contrib/subtree/git-subtree.sh
>>> +++ b/contrib/subtree/git-subtree.sh
>>> @@ -592,7 +592,9 @@ cmd_split()
>>>         eval "$grl" |
>>>         while read rev parents; do
>>>                 revcount=$(($revcount + 1))
>>> -               say -n "$revcount/$revmax ($createcount)
>>> "
>>> +               if [ -z "$quiet" ]; then
>>> +                       printf "%s" "$revcount/$revmax ($createcount)
>>> " >&2
> 
> An additional note for reviewers and appliers: the original and the
> patched codeboth embed a literal ^M,
>...
> whether the code should use some
> escape sequence instead.

As you are using printf, you can easily do:

			printf '%s\r' "..."

without using ^M.

-- Hannes

Re: Fwd: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Matthieu Moy]

Paolo Giarrusso <p.giarrusso@gmail.com> writes:

> Otherwise, one could
> change say to use printf, but that's more invasive.

"invasive" in the sense that it impacts indirectly more callers, but are
there really cases where "echo" is needed when calling "say"? Aren't
there other potential bugs when arbitrary strings are passed to "say",
that would be fixed by using printf once and for all?

The patch would look like the one I did in 89b0230a20 (Wed Aug 7 2013,
die_with_status: use "printf '%s\n'", not "echo").

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Re: Fwd: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Paolo Giarrusso]

On Wed, Oct 9, 2013 at 1:26 PM, Matthieu Moy
<Matthieu.Moy@grenoble-inp.fr> wrote:
> Paolo Giarrusso <p.giarrusso@gmail.com> writes:
>
>> Otherwise, one could
>> change say to use printf, but that's more invasive.
>
> "invasive" in the sense that it impacts indirectly more callers, but are
> there really cases where "echo" is needed when calling "say"? Aren't
> there other potential bugs when arbitrary strings are passed to "say",
> that would be fixed by using printf once and for all?

(1) Changing the implementation of say to use printf "%s\n" would be
trivial, and I think would address your concerns.

But I was concerned about code duplication; one could additionally
make say reusable in this single call site, instead of inlining and
customizing it by replacing the "\n" with "\r". But for that, you need
to either
(2) add an explicit \n to all callers (invasive & error prone), or
(3) make `say` parse the `-n` option and conditionally add "\n" to the
format string or to a final argument, if -n is not specified; this
would affect no current caller, but complicate the implementation of
say. Doing that for just one call site has too much potential for
breakage, so I'm not sure I'd do it. (I'm not even sure on what should
`say` do when `-n` is not the first argument).

Options (1), (2) and (3) are mutually alternative; my favorite is (1).

I can see your points about opportunity, especially after looking at
the commit message of the patch of yours you linked.

> The patch would look like the one I did in 89b0230a20 (Wed Aug 7 2013,
> die_with_status: use "printf '%s\n'", not "echo").

I see your point. But note that using printf like in die_with_status
after that commit wouldn't be reusable here in all call sites, because
it always prints a newline.

Cheers,
-- 
Paolo G. Giarrusso - Ph.D. Student, Philipps-University Marburg
http://www.informatik.uni-marburg.de/~pgiarrusso/

Re: Fwd: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Jeff King]

On Wed, Oct 09, 2013 at 02:03:24PM +0200, Paolo Giarrusso wrote:

> On Wed, Oct 9, 2013 at 1:26 PM, Matthieu Moy
> <Matthieu.Moy@grenoble-inp.fr> wrote:
> > Paolo Giarrusso <p.giarrusso@gmail.com> writes:
> >
> >> Otherwise, one could
> >> change say to use printf, but that's more invasive.
> >
> > "invasive" in the sense that it impacts indirectly more callers, but are
> > there really cases where "echo" is needed when calling "say"? Aren't
> > there other potential bugs when arbitrary strings are passed to "say",
> > that would be fixed by using printf once and for all?
> 
> (1) Changing the implementation of say to use printf "%s\n" would be
> trivial, and I think would address your concerns.

Yeah, I think we should do that. I had the same thought as Matthieu when
I read your initial patch; there are real portability bugs caused by
using "echo" that would be fixed.

However, that is somewhat orthogonal to the bug you are fixing. For
handling this one site, I think it would be fine to just convert it to
use printf, as your patch did. As you noted, the alternatives:

> (2) add an explicit \n to all callers (invasive & error prone), or
> (3) make `say` parse the `-n` option and conditionally add "\n" to the
> format string or to a final argument, if -n is not specified; this
> would affect no current caller, but complicate the implementation of
> say. Doing that for just one call site has too much potential for
> breakage, so I'm not sure I'd do it. (I'm not even sure on what should
> `say` do when `-n` is not the first argument).

...are either annoying or complicated (and in particular, parsing "-n"
means that callers need to be aware that 'say "$foo"' might accidentally
trigger "-n" if $foo comes from the user). So the sanest interface is
probably "say_nonl" or something similar. But since there would only be
one caller, I don't see much point in factoring it out.

> Options (1), (2) and (3) are mutually alternative; my favorite is (1).

Me too. :)

-Peff

Re: Fwd: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Jonathan Nieder]

Paolo Giarrusso wrote:

> Seeing the email, I wonder whether there's hope something like that
> can be preserved in an email, and whether the code should use some
> escape sequence instead.

Yes, please.  Mind if I amend it to

	printf "%s\r" "$revcount/$revmax ($createcount)" >&2

?

[...]
>>         say()
>>         {
>>                 if [ -z "$quiet" ]; then
>>                         echo "$@" >&2
>>                fi
>>         }

I agree with the other reviewers that this should be fixed to use
printf, too, but that's another topic.

Thanks,
Jonathan

Re: Fwd: [PATCH] git-subtree: Avoid using echo -n even indirectly

[Paolo Giarrusso]

On Wed, Oct 9, 2013 at 11:11 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
> Paolo Giarrusso wrote:
>
>> Seeing the email, I wonder whether there's hope something like that
>> can be preserved in an email, and whether the code should use some
>> escape sequence instead.
>
> Yes, please.  Mind if I amend it to
>
>         printf "%s\r" "$revcount/$revmax ($createcount)" >&2
>
> ?

Please do go ahead, by all means (arguably as a different commit, but
those are minor details).

> [...]
>>>         say()
>>>         {
>>>                 if [ -z "$quiet" ]; then
>>>                         echo "$@" >&2
>>>                fi
>>>         }
>
> I agree with the other reviewers that this should be fixed to use
> printf, too, but that's another topic.
Seconded.

-- 
Paolo G. Giarrusso - Ph.D. Student, Philipps-University Marburg
http://www.informatik.uni-marburg.de/~pgiarrusso/