imap-send: Remove limitation on message body

There is a documented limitation on the body of any email not being
able to contain lines starting with "From ". This patch removes that
limitation by improving the parser to search for "From", "Date", and
"Subject" fields in the email before considering it to be an email.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-imap-send.txt

@@ -16,7 +16,9 @@ DESCRIPTION
 This command uploads a mailbox generated with 'git format-patch'
 into an IMAP drafts folder.  This allows patches to be sent as
 other email is when using mail clients that cannot read mailbox
-files directly.
+files directly. The command also works with any general mailbox
+in which emails have the fields "From", "Date", and "Subject" in
+that order.
 
 Typical usage is something like:
 
@@ -118,12 +120,6 @@ Thunderbird in particular is known to be problematic.  Thunderbird
 users may wish to visit this web page for more information:
   http://kb.mozillazine.org/Plain_text_e-mail_-_Thunderbird#Completely_plain_email
 
-
-BUGS
-----
-Doesn't handle lines starting with "From " in the message body.
-
-
 Author
 ------
 Derived from isync 1.0.1 by Mike McCormack.

imap-send.c

@@ -1306,8 +1306,14 @@ static int count_messages(struct msg_data *msg)
 
 	while (1) {
 		if (!prefixcmp(p, "From ")) {
+			p = strstr(p+5, "\nFrom: ");
+			if (!p) break;
+			p = strstr(p+7, "\nDate: ");
+			if (!p) break;
+			p = strstr(p+7, "\nSubject: ");
+			if (!p) break;
+			p += 10;
 			count++;
-			p += 5;
 		}
 		p = strstr(p+5, "\nFrom ");
 		if (!p)