git-prompt: fix reading files with windows line endings

git-prompt: fix reading files with windows line endings

[Robert Abel]

I noticed today that my git prompt using msys-git on Windows got a bit broken.
After investigating I found that the git-prompt doesn't handle the case when
__git_eread reads Windows line endings \r\n. It will only strip \n, leaving
the \r.

I noticed this when I created a repository with msys-git, did some tasks and
later wanted to check the bare. Apparently, another tool on my PC went wild
and replaced all line endings in all text files it could find, breaking my git
prompt.

[PATCH] git-prompt: fix reading files with windows line endings

[Robert Abel]

If any of the files read by __git_eread have \r\n line endings, read
will only strip \n, leaving \r. This results in an ugly prompt, where
instead of

    user@pc MINGW64 /path/to/repo (BARE:master)

the last parenthesis is printed over the beginning of the prompt like

    )ser@pc MINGW64 /path/to/repo (BARE:master

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
 contrib/completion/git-prompt.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index c6cbef38c2..71a64e7959 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -282,7 +282,7 @@ __git_eread ()
 {
 	local f="$1"
 	shift
-	test -r "$f" && read "$@" <"$f"
+	test -r "$f" && read "$@" <"$f" && export $@="${!@%$'\r'}"
 }
 
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
-- 
2.13.0.windows.1

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Johannes Schindelin]

Hi Robert,

On Tue, 28 Nov 2017, Robert Abel wrote:

> If any of the files read by __git_eread have \r\n line endings, read
> will only strip \n, leaving \r. This results in an ugly prompt, where
> instead of
> 
>     user@pc MINGW64 /path/to/repo (BARE:master)
> 
> the last parenthesis is printed over the beginning of the prompt like
> 
>     )ser@pc MINGW64 /path/to/repo (BARE:master

Thats' unfortunate, and obviously something to fix.

> diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
> index c6cbef38c2..71a64e7959 100644
> --- a/contrib/completion/git-prompt.sh
> +++ b/contrib/completion/git-prompt.sh
> @@ -282,7 +282,7 @@ __git_eread ()
>  {
>  	local f="$1"
>  	shift
> -	test -r "$f" && read "$@" <"$f"
> +	test -r "$f" && read "$@" <"$f" && export $@="${!@%$'\r'}"

As far as I understand, $'\r' is a Bash-only construct, and this file
(git-prompt.sh) is targeting other Unix shells, too.

So how about using `tr -d '\r' <"$f" | read "$@"` instead?

Or maybe keep with the Bash construct, but guarded behind a test that we
area actually running in Bash? Something like

	test -z "$BASH" || IFS=$' \t\r\n'

Ciao,
Johannes

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Robert Abel]

Hi Johannes,

On 29 Nov 2017 15:27, Johannes Schindelin wrote:
>> diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
>> index c6cbef38c2..71a64e7959 100644
>> --- a/contrib/completion/git-prompt.sh
>> +++ b/contrib/completion/git-prompt.sh
>> @@ -282,7 +282,7 @@ __git_eread ()
>>  {
>>  	local f="$1"
>>  	shift
>> -	test -r "$f" && read "$@" <"$f"
>> +	test -r "$f" && read "$@" <"$f" && export $@="${!@%$'\r'}"
> 
> As far as I understand, $'\r' is a Bash-only construct, and this file
> (git-prompt.sh) is targeting other Unix shells, too.

Sorry, I wasn't really aware about this bash-ism. I agree that a generic
solution would be best.

> So how about using `tr -d '\r' <"$f" | read "$@"` instead?

That doesn't work for me. Apparently, the variable is always reset to ""
and hence the prompt will always display the shortened sha1.
Maybe it has something to do with variable scoping inside the backtick
evaluation?

> Or maybe keep with the Bash construct, but guarded behind a test that we
> area actually running in Bash? Something like
> 
> 	test -z "$BASH" || IFS=$' \t\r\n'

Actually, this got me thinking and reading the POSIX.1-2008, specifically
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/read.html.

It seems POSIX states that IFS should be supported by read. This means
that it should be okay to just do

> test -r "$f" && IFS=" \t\r\n" read "$@" < "$f"

This would also get rid of the export and avoid introducing backtick
evaluation.

Regards,

Robert

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Johannes Schindelin]

Hi Robert,

On Wed, 29 Nov 2017, Robert Abel wrote:

> On 29 Nov 2017 15:27, Johannes Schindelin wrote:
>
> > Or maybe keep with the Bash construct, but guarded behind a test that we
> > area actually running in Bash? Something like
> > 
> > 	test -z "$BASH" || IFS=$' \t\r\n'
> 
> Actually, this got me thinking and reading the POSIX.1-2008, specifically
> http://pubs.opengroup.org/onlinepubs/9699919799/utilities/read.html.
> 
> It seems POSIX states that IFS should be supported by read.

Yes, that's what I meant: you could use IFS.

> This means that it should be okay to just do
> 
> > test -r "$f" && IFS=" \t\r\n" read "$@" < "$f"

I am afraid that this won't work: when I call

	printf '123\r\n' |
	while IFS=" \t\r\n" read line
	do
		printf '%s' "$line" |
		hexdump -C
	done

it prints

	00000000  31 32 33 0d                               |123.|
	00000004

If I replace the double-quoted IFS by the dollar-single-quoted one, it
works again. I think the reason is that \t, \r and \n are used literally
when double-quoted, not as <HT>, <CR> and <LF>.

Ciao,
Johannes

Re: [PATCH] git-prompt: fix reading files with windows line endings

[SZEDER Gábor]

> > diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
> > index c6cbef38c2..71a64e7959 100644
> > --- a/contrib/completion/git-prompt.sh
> > +++ b/contrib/completion/git-prompt.sh
> > @@ -282,7 +282,7 @@ __git_eread ()
> >  {
> >  	local f="$1"
> >  	shift
> > -	test -r "$f" && read "$@" <"$f"
> > +	test -r "$f" && read "$@" <"$f" && export $@="${!@%$'\r'}"

I don't think that export is necessary here.

> As far as I understand, $'\r' is a Bash-only construct, and this file
> (git-prompt.sh) is targeting other Unix shells, too.

The only other shell the prompt (and completion) script is targeting
is ZSH, and ZSH understands this construct.  We already use this
construct to set IFS in several places in both scripts for a long
time, so it should be fine here, too.


Gábor

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Johannes Schindelin]

[-- Attachment #1: Type: text/plain, Size: 1010 bytes --]

Hi Gábor,

On Thu, 30 Nov 2017, SZEDER Gábor wrote:

> > > diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
> > > index c6cbef38c2..71a64e7959 100644
> > > --- a/contrib/completion/git-prompt.sh
> > > +++ b/contrib/completion/git-prompt.sh
> > > @@ -282,7 +282,7 @@ __git_eread ()
> > >  {
> > >  	local f="$1"
> > >  	shift
> > > -	test -r "$f" && read "$@" <"$f"
> > > +	test -r "$f" && read "$@" <"$f" && export $@="${!@%$'\r'}"
> 
> I don't think that export is necessary here.
> 
> > As far as I understand, $'\r' is a Bash-only construct, and this file
> > (git-prompt.sh) is targeting other Unix shells, too.
> 
> The only other shell the prompt (and completion) script is targeting
> is ZSH, and ZSH understands this construct.  We already use this
> construct to set IFS in several places in both scripts for a long
> time, so it should be fine here, too.

That's good to know! I should have `git grep`ped...

Sorry for the noise,
Johannes

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Robert Abel]

Hi Johannes,

On 30 Nov 2017 01:21, Johannes Schindelin wrote:
> On Wed, 29 Nov 2017, Robert Abel wrote:
>> This means that it should be okay to just do
>>
>>> test -r "$f" && IFS=" \t\r\n" read "$@" < "$f"
> 
> I am afraid that this won't work: when I call

I managed to trick myself with that one, yes...
Apparently I had already converted my HEAD back to Unix line endings.

However, I noticed that the behavior of read is apparently
ambiguous for the last (or a single) variable:

From POSIX.1-2008:
> If there are fewer vars than fields, the last var shall be set to a
> value comprising the following elements:
> - The field that corresponds to the last var in the normal assignment
>   sequence described above
> - The delimiter(s) that follow the field corresponding to the last var
> - The remaining fields and their delimiters, with trailing IFS white
>   space ignored

I read that last "ignored" as "trailing IFS white space shall not be
appended". Apparently, people implementing read read it as "trailing
IFS while space shall not be processed further"

Thus, the behavior for trailing IFS white space is different in
case of one or two variables:

    printf '123 456\r\n' | while IFS=$' \t\r\n' read foo bar
    do
        printf 'foo: %s' "$foo" | hexdump -C
        printf 'bar: %s' "$bar" | hexdump -C
    done

This works as expected trimming the trailing \r:
    00000000  66 6f 6f 3a 20 31 32 33                           |foo: 123|
    00000008
    00000000  62 61 72 3a 20 34 35 36                           |bar: 456|
    00000008

While doing the same just reading a single variable

    printf '123 456\r\n' | while IFS=$' \t\r\n' read foo
    do
        printf 'foo: %s' "$foo" | hexdump -C
        printf 'bar: %s' "$bar" | hexdump -C
    done

prints

    00000000  66 6f 6f 3a 20 31 32 33  20 34 35 36 0d           |foo:
123 456.|
    0000000d
    00000000  62 61 72 3a 20                                    |bar: |
    00000005

Notice the 0d at the end of foo, which didn't get trimmed.

So reading a dummy variable along with the actual content variable
works for git-prompt:

    __git_eread ()
    {
        local f="$1"
        local dummy
        shift
        test -r "$f" && IFS=$'\r\n' read "$@" dummy < "$f"
    }

I feel like this would be the most readable solution thus far.

Regards,

Robert

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Johannes Schindelin]

Hi Robert,

On Thu, 30 Nov 2017, Robert Abel wrote:

> So reading a dummy variable along with the actual content variable
> works for git-prompt:
> 
>     __git_eread ()
>     {
>         local f="$1"
>         local dummy
>         shift
>         test -r "$f" && IFS=$'\r\n' read "$@" dummy < "$f"
>     }
> 
> I feel like this would be the most readable solution thus far.

Hmm. I am just a little concerned about "dummy" swallowing the rest of the
line, e.g. when reading "1 2 3" via `__git_eread line`... the way I read
it, dummy would consume "2 3" and line would *not* receive "1 2 3" but
only "1"...

Ciao,
Johannes

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Robert Abel]

Hi Johannes,

On 30 Nov 2017 16:21, Johannes Schindelin wrote:
> On Thu, 30 Nov 2017, Robert Abel wrote:
>> So reading a dummy variable along with the actual content variable
>> works for git-prompt:
>>
>>     __git_eread ()
>>     {
>>         local f="$1"
>>         local dummy
>>         shift
>>         test -r "$f" && IFS=$'\r\n' read "$@" dummy < "$f"
>>     }
>>
>> I feel like this would be the most readable solution thus far.
> 
> Hmm. I am just a little concerned about "dummy" swallowing the rest of the
> line, e.g. when reading "1 2 3" via `__git_eread line`... the way I read
> it, dummy would consume "2 3" and line would *not* receive "1 2 3" but
> only "1"...
You missed that tab and space aren't field separator anymore,
because IFS=$'\r\n'. The way I see it, __git_eread was never meant to
split tokens. Its primary purpose was to test if a file exists and if
so, read all its contents sans the newline into a variable.

That's how all call to __git_eread use it. And none of them are equipped
to handle multi-line file contents or want to read more than one variable.

So this version does exactly that, but for CRLF line endings, too.
I successfully use the above version now on two of my PCs.

If you agree and nobody else has any concerns, I'll resend an edited
patch to accomodate for the changes and probably put a comment with
usage info above __git_eread.

Regards,

Robert

Re: [PATCH] git-prompt: fix reading files with windows line endings

[SZEDER Gábor]

On Thu, Nov 30, 2017 at 2:51 AM, Johannes Schindelin
<Johannes.Schindelin@gmx.de> wrote:
> On Thu, 30 Nov 2017, SZEDER Gábor wrote:
>
>> > > diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
>> > > index c6cbef38c2..71a64e7959 100644
>> > > --- a/contrib/completion/git-prompt.sh
>> > > +++ b/contrib/completion/git-prompt.sh
>> > > @@ -282,7 +282,7 @@ __git_eread ()
>> > >  {
>> > >   local f="$1"
>> > >   shift
>> > > - test -r "$f" && read "$@" <"$f"
>> > > + test -r "$f" && read "$@" <"$f" && export $@="${!@%$'\r'}"
>>
>> I don't think that export is necessary here.
>>
>> > As far as I understand, $'\r' is a Bash-only construct, and this file
>> > (git-prompt.sh) is targeting other Unix shells, too.
>>
>> The only other shell the prompt (and completion) script is targeting
>> is ZSH, and ZSH understands this construct.  We already use this
>> construct to set IFS in several places in both scripts for a long
>> time, so it should be fine here, too.
>
> That's good to know! I should have `git grep`ped...
>
> Sorry for the noise,

No, no, your concern is justified, you just happened to pick the wrong
construct :)

It's the ${!var} indirect expansion construct that ZSH doesn't know, it
uses a different syntax for that.


Gábor

Re: [PATCH] git-prompt: fix reading files with windows line endings

[Johannes Schindelin]

Hi Robert,

On Thu, 30 Nov 2017, Robert Abel wrote:

> On 30 Nov 2017 16:21, Johannes Schindelin wrote:
> > On Thu, 30 Nov 2017, Robert Abel wrote:
> >> So reading a dummy variable along with the actual content variable
> >> works for git-prompt:
> >>
> >>     __git_eread ()
> >>     {
> >>         local f="$1"
> >>         local dummy
> >>         shift
> >>         test -r "$f" && IFS=$'\r\n' read "$@" dummy < "$f"
> >>     }
> >>
> >> I feel like this would be the most readable solution thus far.
> > 
> > Hmm. I am just a little concerned about "dummy" swallowing the rest of the
> > line, e.g. when reading "1 2 3" via `__git_eread line`... the way I read
> > it, dummy would consume "2 3" and line would *not* receive "1 2 3" but
> > only "1"...
> You missed that tab and space aren't field separator anymore,
> because IFS=$'\r\n'. The way I see it, __git_eread was never meant to
> split tokens. Its primary purpose was to test if a file exists and if
> so, read all its contents sans the newline into a variable.

Ah. The "$@* put me on the wrong track. If you hard-code the expectation
that __git_eread is not used to split tokens, maybe there should be a
preparatory patch (after carefully ensuring that all callers pass only one
argument) to change the "$@" to "$1"?

That will prevent future callers from expecting the token-splitting
behavior that is promised by using "$@".

Ciao,
Johannes

[PATCH v2 1/2] git-prompt: make __git_eread intended use explicit

[Robert Abel]

__git_eread is used to read a single line of a given file (if it exists)
into a variable without the EOL. All six current users of __git_eread
use it that way and don't expect multi-line content.

Thus, add a comment and explicitly use $2 instead of shifting the args
down and using $@.

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
 contrib/completion/git-prompt.sh | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index c6cbef38c..41a471957 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -278,11 +278,12 @@ __git_ps1_colorize_gitstring ()
 	r="$c_clear$r"
 }
 
+# Helper function to read the first line of a file into a variable.
+# __git_eread requires 2 arguments, the file path and the name of the
+# variable, in that order.
 __git_eread ()
 {
-	local f="$1"
-	shift
-	test -r "$f" && read "$@" <"$f"
+	test -r "$1" && read "$2" <"$1"
 }
 
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
-- 
2.15.1

[PATCH v2 2/2] git-prompt: fix reading files with windows line endings

[Robert Abel]

If any of the files read by __git_eread have \r\n line endings, read
will only strip \n, leaving \r. This results in an ugly prompt, where
instead of

    user@pc MINGW64 /path/to/repo (BARE:master)

the last parenthesis is printed over the beginning of the prompt like

    )ser@pc MINGW64 /path/to/repo (BARE:master

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
 contrib/completion/git-prompt.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 41a471957..983e419d2 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -283,7 +283,7 @@ __git_ps1_colorize_gitstring ()
 # variable, in that order.
 __git_eread ()
 {
-	test -r "$1" && read "$2" <"$1"
+	test -r "$1" && IFS=$'\r\n' read "$2" <"$1"
 }
 
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
-- 
2.15.1

Re: [PATCH v2 2/2] git-prompt: fix reading files with windows line endings

[Johannes Schindelin]

[-- Attachment #1: Type: text/plain, Size: 714 bytes --]

Hi Robert,

1/2 looks very good.

On Sat, 2 Dec 2017, Robert Abel wrote:

> If any of the files read by __git_eread have \r\n line endings, read
> will only strip \n, leaving \r. This results in an ugly prompt, where
> instead of
> 
>     user@pc MINGW64 /path/to/repo (BARE:master)
> 
> the last parenthesis is printed over the beginning of the prompt like
> 
>     )ser@pc MINGW64 /path/to/repo (BARE:master

Maybe mention explicitly what Gabór said about $'...' being supported by
Bash and zsh, the only two intended users of git-prompt.sh (and there
being precedent of that construct being used already e.g. in __git_ps1)?

Other than that, this looks very good to me.

Thanks,
Johannes

Re: [PATCH v2 1/2] git-prompt: make __git_eread intended use explicit

[Junio C Hamano]

Robert Abel <rabel@robertabel.eu> writes:

> __git_eread is used to read a single line of a given file (if it exists)
> into a variable without the EOL. All six current users of __git_eread
> use it that way and don't expect multi-line content.

Changing $@ to $2 does not change whether this is about "multi-line"
or not.  What you are changing is that the original was prepared to
be given two or more variable names, and split an input line at IFS
into multiple tokens to be assigned to these variables, but with
this change, the caller can only use one variable and this function
will not split the line and store it into that single variable.

The above can easily be fixed with a bit of rewording, perhaps like:

    ... that way.  We do not need to split the line into tokens and
    assign them to multiple variables---reading only into a single
    variable needs to be supported.

While reviewing this patch, I also wondered if the "read" wants to
become "read -r" or something that is even safer than simply
avoiding tokenization, but after scanning to see exactly which files
__git_eread is used to read from, I do not think it matters (the
input will not have a backslash that would want to be protected from
'read'), so this should be OK.

> Signed-off-by: Robert Abel <rabel@robertabel.eu>
> ---
>  contrib/completion/git-prompt.sh | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
> index c6cbef38c..41a471957 100644
> --- a/contrib/completion/git-prompt.sh
> +++ b/contrib/completion/git-prompt.sh
> @@ -278,11 +278,12 @@ __git_ps1_colorize_gitstring ()
>  	r="$c_clear$r"
>  }
>  
> +# Helper function to read the first line of a file into a variable.
> +# __git_eread requires 2 arguments, the file path and the name of the
> +# variable, in that order.
>  __git_eread ()
>  {
> -	local f="$1"
> -	shift
> -	test -r "$f" && read "$@" <"$f"
> +	test -r "$1" && read "$2" <"$1"
>  }
>  
>  # __git_ps1 accepts 0 or 1 arguments (i.e., format string)

Re: [PATCH v2 1/2] git-prompt: make __git_eread intended use explicit

[Robert Abel]

Hi Junio,

On 04 Dec 2017 18:58, Junio C Hamano wrote:
> Robert Abel <rabel@robertabel.eu> writes:
>> __git_eread is used to read a single line of a given file (if it exists)
>> into a variable without the EOL. All six current users of __git_eread
>> use it that way and don't expect multi-line content.
> 
> Changing $@ to $2 does not change whether this is about "multi-line"
> or not. 

I'm aware of that. I was documenting current usage. The function is used
to read file contents (which are expected to be a single line) into
_a_ (i.e. single) variable.

None of the current users of the function expect tokens to be split,
which is why I removed it in preparation of patch 2/2, which would
break tokenizing file contents.

Regards,

Robert

[PATCH v3 1/2] git-prompt: make __git_eread intended use explicit

[Robert Abel]

__git_eread is used to read a single line of a given file (if it exists)
into a single variable without the EOL. All six current users of __git_eread
use it that way and don't expect multi-line content.

Therefore, this patch removes the unused capability to split file conents into
tokens by passing multiple variable names. Add a comment and explicitly use $2
instead of $@ to read the file into one variable.

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
 contrib/completion/git-prompt.sh | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index c6cbef38c2..41a471957a 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -278,11 +278,12 @@ __git_ps1_colorize_gitstring ()
 	r="$c_clear$r"
 }
 
+# Helper function to read the first line of a file into a variable.
+# __git_eread requires 2 arguments, the file path and the name of the
+# variable, in that order.
 __git_eread ()
 {
-	local f="$1"
-	shift
-	test -r "$f" && read "$@" <"$f"
+	test -r "$1" && read "$2" <"$1"
 }
 
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
-- 
2.13.0.windows.1

[PATCH v3 2/2] git-prompt: fix reading files with windows line endings

[Robert Abel]

If any of the files read by __git_eread have \r\n line endings, read
will only strip \n, leaving \r. This results in an ugly prompt, where
instead of

    user@pc MINGW64 /path/to/repo (BARE:master)

the last parenthesis is printed over the beginning of the prompt like

    )ser@pc MINGW64 /path/to/repo (BARE:master

This patch fixes the issue by setting the IFS to $'\r\n' for the read
operation. Note that ANSI-C Quoting ($'...') is supported by bash as
well as zsh, which are the current targets of git-prompt.sh, cf.
<20171130010811.17369-1-szeder.dev@gmail.com>.

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
 contrib/completion/git-prompt.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 41a471957a..983e419d2b 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -283,7 +283,7 @@ __git_ps1_colorize_gitstring ()
 # variable, in that order.
 __git_eread ()
 {
-	test -r "$1" && read "$2" <"$1"
+	test -r "$1" && IFS=$'\r\n' read "$2" <"$1"
 }
 
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
-- 
2.13.0.windows.1

Re: [PATCH v2 1/2] git-prompt: make __git_eread intended use explicit

[Junio C Hamano]

Robert Abel <rabel@robertabel.eu> writes:

> Hi Junio,
>
> On 04 Dec 2017 18:58, Junio C Hamano wrote:
>> Robert Abel <rabel@robertabel.eu> writes:
>>> __git_eread is used to read a single line of a given file (if it exists)
>>> into a variable without the EOL. All six current users of __git_eread
>>> use it that way and don't expect multi-line content.
>> 
>> Changing $@ to $2 does not change whether this is about "multi-line"
>> or not. 
>
> I'm aware of that. I was documenting current usage. The function is used
> to read file contents (which are expected to be a single line) into
> _a_ (i.e. single) variable.
>
> None of the current users of the function expect tokens to be split,
> which is why I removed it in preparation of patch 2/2, which would
> break tokenizing file contents.

I know all of the above, but I think you misunderstood the point I
wanted to raise, so let me try again.  The thing is, none of what
you just wrote changes the fact that lack of callers that want to do
"multi-line" is IRRELEVANT.  True, there is no caller that wants to
read multiple lines---it is a true statement, but it is irrelevant
statement.  On the other hand, it is true and relevant that no
caller expects to split a line into multiple variables.

By changing "$@" to "$2" there, you would have broken callers that
wanted the helper function to read into multiple variables (if there
were such callers).  Explaining the current usage that nobody does
so *IS* a valid justification for the change.  It is relevant.

With or without that change, a caller that wanted to read multiple
lines from the file would never have worked.  It was just doing a
single "read" built-in, so the only thing that would have been
worked on is the first line of the file.  Your change wouldn't have
changed that---if a caller wanted to peek into the second line, your
change wouldn't have helped such a caller.  And it is not like your
change would have broken such a caller that were happily reading the
second and subsequent line.  The original wouldn't allowed it to
read the second line anyway.

Contrasting this with the above obsesrvation about possible breakage
for multi-variable callers (if there were such callers---luckily
there wasn't any), I hope that you can see why the lack of
"multi-line" caller in the existing usage is totally irrelevant when
analyzing this change and explaining why this is a good change.

HTH.

Re: [PATCH v2 1/2] git-prompt: make __git_eread intended use explicit

[Robert Abel]

Hi Junio,

On 05 Dec 2017 01:27, Junio C Hamano wrote:
> I know all of the above, but I think you misunderstood the point I
> wanted to raise, so let me try again.  The thing is, none of what
> you just wrote changes the fact that lack of callers that want to do
> "multi-line" is IRRELEVANT.

I disagree. The commit comment is meant to give context to the
introduced changes. One change is the  additional comment for
__git_eread, which now clearly states that only a single line is read.

I'm well aware that I'm not breaking reading multiple lines, because
that never worked in the first place. Thus, it was never the indented
use for __git_eread as I see it. I explicitly want to include that
information in my commit message to pay it forward to the next person
working on the prompt.

Regards,

Robert

Re: [PATCH v2 1/2] git-prompt: make __git_eread intended use explicit

[Junio C Hamano]

Robert Abel <rabel@robertabel.eu> writes:

> On 05 Dec 2017 01:27, Junio C Hamano wrote:
>> I know all of the above, but I think you misunderstood the point I
>> wanted to raise, so let me try again.  The thing is, none of what
>> you just wrote changes the fact that lack of callers that want to do
>> "multi-line" is IRRELEVANT.
>
> I disagree. The commit comment is meant to give context to the
> introduced changes. One change is the  additional comment for
> __git_eread, which now clearly states that only a single line is read.

I still do not understand why you think the 'next' person would care
about the (lack of )multi-line aspect of the helper.

Let's see how well the proposed log message gives the "context to
the introduced changes" (from your v3).

    __git_eread is used to read a single line of a given file (if it
    exists) into a single variable without the EOL. All six current
    users of __git_eread use it that way and don't expect multi-line
    content.

That does not include anything incorrect; but.

The helper is about (1) reading the first line and (2) reading it as
a whole into a single variable.  Both are already covered by the
first sentence, and there is no need to say 'and don't expect ...",
unless you want to stress something.

And it places a stress on the former, which is a less relevant
thing, WITHOUT giving the same treatment to the latter, which is a
more relevant thing.  After all, this patch is not about replacing
an earlier implementation that did

    $2=$(cat "$1")

with

    read $2 <"$1"

If that were the case, _then_ the fact that the purpose of the
helper is to read from a single-liner file (i.e. we do not expect
the input file to have more than one line) is VERY relevant.

But this is not such a patch.  And after readers read the above,
they find this:

    Therefore, this patch removes the unused capability to split
    file conents into tokens by passing multiple variable names.

And because the previous paragraph placed an emphasis on a wrong
aspect of the context of the calls to the helper function, this
"Therefore" does not quite "click" in the readers' minds.  The
reason why it is OK to remove the multi-variable feature is because
the callers of the helper want to always read the result into a
single variable, but the "no need for multi-variable" that they read
in the first sentence of the previous paragraph is less strong in
their mind by now, because they read an irrelevant (for the purpose
of this "Therefore") mention of "no need for multi-line" aspect of
the helper.

Perhaps

    __git_eread is used to read the contents of a single-liner file
    into a single variable while dropping EOL.  It is misleading to
    use the "read" built-in with "$@", as if some callers would want
    the contents read from the file to be split into multiple
    variables.

    Explicitly use a single variable, and also document that the
    helper only reads the first line (simply because the input files
    are designed to be single-liner files).

would say it the same thing, but with emphasis on the right aspect
of the facts.

I would also rephase the new in-code comment

    # Helper function to read the first line of a file into a variable.

to un-stress "the first line of a file" and place more stress on the
fact that it is designed to read from a single-liner file (there is
a subtle but important distinction between the two).

    # read the contents of a single-liner file into a variable,
    # while dropping the end-of-line from it.

or something like that, perhaps.

Re: [PATCH v2 1/2] git-prompt: make __git_eread intended use explicit

[Robert Abel]

Dear Junio,

I'm amazed at how much time and energy you spend on correcting these
essentially non-issues in my git commit messages for a quadruple-liner
code change.

I'll resend both patches one last time addressing the grave issue of the
informative mention of multi-line files.

Regards,

Robert

[PATCH v4 1/2] git-prompt: make __git_eread intended use explicit

[Robert Abel]

__git_eread is used to read a single line of a given file (if it exists)
into a single variable stripping the EOL.
This patch removes the unused capability to split file contents into tokens
by passing multiple variable names. Add a comment and explicitly use $2
instead of misleading $@ as argument to the read builtin command.

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
 contrib/completion/git-prompt.sh | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index c6cbef38c2..41a471957a 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -278,11 +278,12 @@ __git_ps1_colorize_gitstring ()
 	r="$c_clear$r"
 }
 
+# Helper function to read the first line of a file into a variable.
+# __git_eread requires 2 arguments, the file path and the name of the
+# variable, in that order.
 __git_eread ()
 {
-	local f="$1"
-	shift
-	test -r "$f" && read "$@" <"$f"
+	test -r "$1" && read "$2" <"$1"
 }
 
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
-- 
2.13.0.windows.1

[PATCH v4 2/2] git-prompt: fix reading files with windows line endings

[Robert Abel]

If any of the files read by __git_eread have \r\n line endings, read
will only strip \n, leaving \r. This results in an ugly prompt, where
instead of

    user@pc MINGW64 /path/to/repo (BARE:master)

the last parenthesis is printed over the beginning of the prompt like

    )ser@pc MINGW64 /path/to/repo (BARE:master

This patch fixes the issue by changing the internal field separator
variable IFS to $'\r\n' before using the read builtin command.

Note that ANSI-C Quoting/POSIX Quoting ($'...') is supported by bash
as well as zsh, which are the current targets of git-prompt, cf.
contrib/completion/git-prompt.sh.

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
 contrib/completion/git-prompt.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 41a471957a..983e419d2b 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -283,7 +283,7 @@ __git_ps1_colorize_gitstring ()
 # variable, in that order.
 __git_eread ()
 {
-	test -r "$1" && read "$2" <"$1"
+	test -r "$1" && IFS=$'\r\n' read "$2" <"$1"
 }
 
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
-- 
2.13.0.windows.1