Re: [PATCH] generate a valid rfc2047 mail header for multi-line subject.

xzer [off-list ref] writes:

Subject: Re: [PATCH] generate a valid rfc2047 mail header for multi-line subject.

We prefer to have "[PATCH] subsystem: description without final full-stop" here.

There is still a problem that git-am will lost the line break.

What does "still" refer to?  It is unclear under what condition the
command lose "the line break" (nor which line break you are refering to; I
am guessing that you have a commit that begins with a multi-line paragraph
and you are talking about line breaks between the lines in the first
paragraph).

It's not easy to retain it, but as the first step, we can generate
a valid rfc2047 header now.

Please describe what is broken (iow, "Given this sample input, we
currently generate this output, which is not a valid rfc2047") and what
the new output looks like ("Update pp_title_line() to generate this output
instead.")

---

Missing sign-off with a real name.

You seem to have indent that uses SPs instead of HT around here...

+                linelen = get_one_line(cline);

I can see you are trying to be careful not to let get_one_line() overstep
past "len" the caller gave you by making a copy first, but is this
overhead really necessary?  After all we know in this static function that
the caller is feeding the contents from a strbuf, which always have a
terminating NUL (and that is why it is Ok that get_one_line() is not a
counted string interface).

+
+                cline += linelen;
+
+                if (!linelen)
+                        break;
+		
+		if (!first)
+			strbuf_addf(sb, "\n ");
+
+		offset = *(cline -1) == '\n'; 
+
+		add_rfc2047(sb, cline-linelen, linelen-offset, encoding);
+		first = 0;
+
+        }
+	free(mline);
+}

So the general idea of this change (I am thinking aloud what should be in
the updated commit log message as the problem description) is that:

 - We currently give an entire multi-line paragraph string to the
   add_rfc2047() function to be formatted as the title of the commit;

 - The add_rfc2047() functionjust passes "\n" through, without making it a
   folding whitespace followed by a newline, to help callers that want to
   use this function to produce a header line that is rfc 2822 conformant;

 - The patch introduces a new function add_rfc2047_multiline() that splits
   its input and performs line folding for such a caller (namely, the
   pp_title_line() function);

 - Another caller of add_rfc2047(), pp_user_info, is not changed, and it
   won't fold the name of the user that appear on the From: line.

It is unclear if the last point is really the right thing to do, though.
It is not a new problem that an author name that has a "\n" in it would
break the output, but we probably would want to fix that case too here?