Allow commenting tickets via mail

[strk]

It would be useful to be able to reply to email notified upon ticket activity.
This is more or less what's requested to Gogs via gogs/gogs#2602 (comment)

It could be some gitea readmail comand reading a message from stdin, letting system administrators configure an email address forwarded to the command (would be easy in unix world). Implies holding a database with identifiers for threads/users to match.

[tboerger]

Not an easy task because multiple input ways have to be covered.

[Josue-T]

Hello,

Maybe the solution would be to add some parameter to access a pop3 mailbox and gitea will retrieve each 5 minutes the mailbox content. This way was already implemented in forum discurse.

[lafriks]

Or we could add smtp server to gitea :]

[lunny]

@lafriks We just need to check email via pop/IMAP protocol.

[lunny]

The problem is how we recognize which email is a comment to which repository's which issue. We need make a rule.

[ptman]

In-Reply-To or References header that matches an email that was sent from the issue? http://jkorpela.fi/headers.html

[lunny]

It seems right. We can include a header in the email we sent. But when user reply to this email, if the header will be copied to the reply email?

[a1012112796]

That's right. Here is the message in github email, may be we can try same style ... ``` Date: Sun, 19 Apr 2020 07:43:39 -0700 From: Lunny Xiao <notifications@github.com&gt; Reply-To: go-gitea/gitea <reply@reply.github.com&gt; To: go-gitea/gitea <gitea@noreply.github.com&gt; Cc: Subscribed <subscribed@noreply.github.com&gt; Message-ID: <go-gitea/gitea/issues/745/616150955@github.com&gt; In-Reply-To: <go-gitea/gitea/issues/745@github.com&gt; References: <go-gitea/gitea/issues/745@github.com&gt; Subject: Re: [go-gitea/gitea] Allow commenting tickets via mail (#745) Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="--==_mimepart_5e9c639bb9db_2ac03fa88d0cd9681698d"; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: list X-GitHub-Sender: lunny X-GitHub-Recipient: a1012112796 X-GitHub-Reason: subscribed List-ID: go-gitea/gitea <gitea.go-gitea.github.com&gt; List-Archive: https://github.com/go-gitea/gitea List-Post: <mailto:reply@reply.github.com&gt; List-Unsubscribe: <mailto:unsub+AGBLDSVFHOXULGY25KN7O554VBCJXEVBNHHAYF6MYI@reply.github.com&gt;, <https://github.com/notifications/unsubscribe/AGBLDSQ4RV7B75FDV4HYPQLRNMEZXANCNFSM4C5SGZ3A&gt; X-Auto-Response-Suppress: All X-GitHub-Recipient-Address: 1012112796@qq.com ``` and it has a fast reply button, which I used now. I think It's also usefull.

…

------------------&nbsp;原始邮件&nbsp;------------------ 发件人: "Lunny Xiao"<notifications@github.com&gt;; 发送时间: 2020年4月19日(星期天) 晚上10:43 收件人: "go-gitea/gitea"<gitea@noreply.github.com&gt;; 抄送: "Subscribed"<subscribed@noreply.github.com&gt;; 主题: Re: [go-gitea/gitea] Allow commenting tickets via mail (#745) It seems right. We can include a header in the email we sent. But when user reply to this email, if the header will be copied to the reply email? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or unsubscribe.

[a1012112796]

Here is my first time to try email reply in github, I found the commet published by email is more slow to show on ui than comment directly . so maybe github also did the same things which we thinking :)

[a1012112796]

maybe we have send replies message now ...

gitea/services/mailer/mail.go

Lines 249 to 258 in 9f959ac

	// Set Message-ID on first message so replies know what to reference
	if actName == "new" {
	msg.SetHeader("Message-ID", "<"+ctx.Issue.ReplyReference()+">")
	} else {
	msg.SetHeader("In-Reply-To", "<"+ctx.Issue.ReplyReference()+">")
	msg.SetHeader("References", "<"+ctx.Issue.ReplyReference()+">")
	}
	msgs = append(msgs, msg)
	}

So maybe only need to add something to recive email 😊
@lunny

[strk]

A gitea commandline argument to "parse mail" would be enough for a
start. A system administrator would setup their favorite mechanism
to receive mail and would pipe the mail content to such new
commandline.