Re: [BUG?] iconv used as textconv, and spurious ^M on added lines on Windows

["Jakub Narębski" <jnareb@gmail.com>]

W dniu 31.03.2017 o 14:38, Torsten Bögershausen pisze:
> On 30.03.17 21:35, Jakub Narębski wrote:
>> Hello,
>>
>> Recently I had to work on a project which uses legacy 8-bit encoding
>> (namely cp1250 encoding) instead of utf-8 for text files (LaTeX
>> documents).  My terminal, that is Git Bash from Git for Windows is set
>> up for utf-8.
>>
>> I wanted for "git diff" and friends to return something sane on said
>> utf-8 terminal, instead of mojibake.  There is 'encoding'
>> gitattribute... but it works only for GUI ('git gui', that is).
>>
>> Therefore I have (ab)used textconv facility to convert from cp1250 of
>> file encoding to utf-8 encoding of console.
>>
>> I have set the following in .gitattributes file:
>>
>>   ## LaTeX documents in cp1250 encoding
>>   *.tex text diff=mylatex
>>
>> The 'mylatex' driver is defined as:
>>
>>   [diff "mylatex"]
>>         xfuncname = "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$"
>>         wordRegex = "\\\\[a-zA-Z]+|[{}]|\\\\.|[^\\{}[:space:]]+"
>>         textconv  = \"C:/Program Files/Git/usr/bin/iconv.exe\" -f cp1250 -t utf-8
>>         cachetextconv = true
>>
>> And everything would be all right... if not the fact that Git appends
>> spurious ^M to added lines in the `git diff` output.  Files use CRLF
>> end-of-line convention (the native MS Windows one).
>>
>>   $ git diff test.tex
>>   diff --git a/test.tex b/test.tex
>>   index 029646e..250ab16 100644
>>   --- a/test.tex
>>   +++ b/test.tex
>>   @@ -1,4 +1,4 @@
>>   -\documentclass{article}
>>   +\documentclass{mwart}^M
>>   
>>    \usepackage[cp1250]{inputenc}
>>    \usepackage{polski}
>>
>> What gives?  Why there is this ^M tacked on the end of added lines,
>> while it is not present in deleted lines, nor in content lines?
>>
>> Puzzled.
>>
>> P.S. Git has `i18n.commitEncoding` and `i18n.logOutputEncoding`; pity
>> that it doesn't supports in core `encoding` attribute together with
>> having `i18n.outputEncoding`.
>
> Is there a chance to give us a receipt how to reproduce it?
> A complete test script or ?
> (I don't want to speculate, if the invocation of iconv is the problem,
>  where stdout is not in "binary mode", or however this is called under Windows)

I'm sorry, I though I posted whole recipe, but I missed some details
in the above description of the case.

First, files are stored on filesystem using CRLF eol (DOS end-of-line
convention).  Due to `core.autocrlf` they are converted to LF in blobs,
that is in the index and in the repository.

Second, a textconv with filter preserving end-of-line needs to be
configured.  I have used `iconv`, but I suspect that the problem would
happen also for `cat`.

In the .gitattributes file, or .git/info/attributes add, for example:

  *.tex text diff=myconv

In the .git/config configure the textconv filter, for example:

  [diff "myconv"]
         textconv  = iconv.exe -f cp1250 -t utf-8

Create a file which filename matches the attribute line, and which
uses CRLF end of line convention, and add it to Git (adding it to
the index):

  $ printf "foo\r\n" >foo.tex
  $ git add foo.tex

Modify file (also with CRLF):

  $ printf "bar\r\n" >foo.tex

Check the difference

  $ git diff foo.tex

HTH
-- 
Jakub Narębski