abnormal parse when cfg came from a file

Hello,

On windows, i wish to upload "c:\autoexec.bat" file

on 7.25.0 we can see first test was good and second test was bad, he
tries to login and
upload "c:autoexec.bat" instead of "c:\autoexec.bat"

on 7.26.0 we can see first test was always good and second test was bad,
he refuses 
to login because "c:autoexec.bat" does not exist

the trouble on these 2 versions was the config file is parsed and lose a
"\" sign, why ?

D:\>c:\html\$test\communs\curl.exe ftp://ftpperso.free.fr -u
vivil:secret -K config [...]
curl: Can't open 'c:autoexec.bat'!
curl: try 'curl --help' or 'curl --manual' for more information

********************************************************
set host=ftpperso.free.fr
set user=vivil
set pass=secret
set file=c:\autoexec.bat
del aaa
del config
del log?.txt
c:\html\$test\communs\curl.exe ftp://%host% -u %user%:%pass% -T "%file%"
--trace-ascii log1.txt
find "data connection for" log1.txt > log3.txt
echo upload-file="%file%" > config
c:\html\$test\communs\curl.exe ftp://%host% -u %user%:%pass% -K config
--trace-ascii log2.txt
find "data connection for" log2.txt >> log3.txt
type log3.txt
pause

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