Re: [Bug] git branch -v has problems with carriage returns

From: Atousa Duprat <atousa.p@gmail.com>
Date: May 31, 2017, 05:32 UTC
Message-ID: <CA+izobteEUSisKXNr=k5BcN9hVV4nyqYPWuRLAgV-rg9chH4_g@mail.gmail.com>
In-Reply-To: <3d02b958-5f72-9676-bce9-afca962c07df@kdbg.org>

Here is my first attempt at fixing the issue.

There are two problems in ref-filter.c:

First, copy_subject() has been modified to turn '\n' into a space and every other ascii control character to be ignored.

Second, find_subpos() doesn't realize that a line that only contains a '\r\n' is a blank line – at least when using crlf convention. I have changed things so that a sequence of either '\n' or "\r\n" separate the subject from the body of the commit message. I am not looking at the crlf setting because it doesn't seem like a useful distinction – when one would we ever care for \r\n not to be a blank line? But it could be done...

Both fixes are minimal, but it feels like they are a issues with the specific encoding. Does git mandate ascii or utf-8 commit messages? If not, there may be a larger issue here with encodings and line-end conventions at the very least in ref-filter.c Guidance would be appreciated for how to deal with this issue...

Patch attached.

Atousa

On Fri, May 19, 2017 at 11:48 PM, Johannes Sixt <j6t@kdbg.org> wrote:

Show 36 quoted lines

> Am 19.05.2017 um 23:55 schrieb Atousa Duprat:
>>
>> I have tried to repro this issue but git goes out of its way to store
>> the commit messages using unix end-of-line format.
>> I think that git itself cannot create a repo exhibiting this problem.
>
>
> Here is a recipe to reproduce the error:
>
>   git init
>   git commit --allow-empty -m initial
>   git branch crlf $(printf '%s\r\n' subject '' line3_long line4 |
>        git commit-tree HEAD:)
>
> The reason for the "bug" is obviously that a line having CR in addition to
> LF is not "an empty line". Consequently, the second line is not treated as a
> separator between subject and body, whereupon Git concatenates all lines
> into one large subject line. This strips the LFs but leaves the CRs in tact,
> which, when printed on a terminal move the cursor to the beginning of the
> line, so that text after the CRs overwrites what is already in the terminal.
>
> This is just to give you a head start. I'm not going to look into this.
>
> -- Hannes
>
>
>>> If I do `git branch -v` with such a subject line somehow the third and
>>> second line get combined before the hash. Example:
>>>
>>> $ git branch -v
>>> See merge request !XXXX temp space 84e18d22fd Merge branch
>>> 'feature-XXX' into 'develop'
>>> # <begins with third line> <ending of seconds line (if longer than
>>> third)> <commit hash (correct)> <subject line (correct)>
>>>
>>> Before git v2.13.0 `git branch -v` worked completely normal.

diff --git a/ref-filter.c b/ref-filter.c
index 3a640448f..bc573f481 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -836,11 +836,15 @@ static const char *copy_email(const char *buf)
 static char *copy_subject(const char *buf, unsigned long len)
 {
 	char *r = xmemdupz(buf, len);
-	int i;
+	int i, j;
 
-	for (i = 0; i < len; i++)
+	for (i = 0, j = 0; i < len; i++, j++)
 		if (r[i] == '\n')
-			r[i] = ' ';
+			r[j] = ' ';
+		else if (r[i] < 32)
+                    j--; // skip ascii control characters that are not '\n'
+                else r[j] = r[i];
+        r[j]=0;
 
 	return r;
 }
@@ -956,9 +960,12 @@ static void find_subpos(const char *buf, unsigned long sz,
 			eol++;
 		buf = eol;
 	}
+
 	/* skip any empty lines */
 	while (*buf == '\n')
 		buf++;
+	while (*buf == '\r' && *(buf+1) == '\n')
+		buf += 2;
 
 	/* parse signature first; we might not even have a subject line */
 	*sig = buf + parse_signature(buf, strlen(buf));