feat: flag what you answered, mark what was forwarded to you

Item 68, which turned out to be three things once its premise was
measured. The note asked to extend a "passed" subject rule to "Fw:";
there was no subject rule, and the correlation it rested on did not
exist. What did exist was a gap nobody had reported.

Reply and forward now flag their source. The Maildir R and P flags,
which every other client sets and notmuch reads back as "replied" and
"passed", had never been written here: measured on the developer's
index, all 317 "replied" and all 6 "passed" came from other clients.
ComposeWindow emits sourceMessageAnswered after a successful send and
MainWindow routes it through sendMessageTagChange, message-scoped and
off the undo stack, for the reason auto mark-read is: the flag records
that the mail went, and the send cannot be undone.

ComposeContext carries sourceMessageId rather than reusing inReplyTo,
which is deliberately empty on a forward so the recipient's client does
not file it under the thread it left. Keying on it made the "passed"
half dead code that compiled and never fired. A resumed draft is
excluded: its kind records how the file was opened, not what the user is
doing, so flagging on it would set R from a guess.

A received forward gets its own mark. Derived from the subject at paint
time, storing nothing and reaching no server, because "passed" means "I
forwarded this" and setting it from a guess would assert something false
on 222 existing messages. subjectIsForwarded() shares forwardSubject()'s
prefix table so the two cannot disagree, strips a Re: chain first, and
takes extra locale spellings from [general] forward_prefixes, which
extends the built-in table rather than replacing it.

A mutation survived the first round and corrected a claim in the code:
QRegularExpression::escape already makes a punctuation prefix inert, so
the word guard is not about pattern validity. It stops a configured "-"
matching "-: x". The comment and test say that now.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LXCZFLXbAii5n5wtovpdhh

1 files changed, 16 insertions, 0 deletions

diff --git a/src/config.h b/src/config.h
index 02b4038..26fc1c1 100644
--- a/src/config.h
+++ b/src/config.h
@@ -349,6 +349,14 @@ public:
     /// account that configures no sent folder would show the entire Maildir.
     static QString matchNothingQuery();
 
+    /// The tag a built-in generator matches, or empty for the folder-backed
+    /// ones (`sent`, `drafts`, `trash`) which compose from a path instead.
+    ///
+    /// Exposed so a caller asking "which tag decides membership of this view"
+    /// reads the same table the query generator does, rather than keeping a
+    /// second copy that can drift from it.
+    static QString generatorTagFor(const QString &generator);
+
     /// Empty when unset; the caller disables the Sync button in that case.
     QString syncCommand() const { return m_syncCommand; }
 
@@ -412,6 +420,13 @@ public:
     /// the same fixed string on every card rather than failing visibly.
     QString dateFormat() const { return m_dateFormat; }
 
+    /// Extra subject prefixes marking a forward the user RECEIVED (item 68).
+    ///
+    /// Added to the built-in table in composecontext.cpp, never replacing it,
+    /// so a user adding a locale keeps the measured English/German/Iberian/
+    /// French spellings. Bare words, no colon.
+    QStringList forwardPrefixes() const { return m_forwardPrefixes; }
+
     /// Interface language, or empty to follow the environment.
     ///
     /// A locale name, short ("it") or full ("it_IT"); Qt resolves the short
@@ -536,6 +551,7 @@ private:
     int m_toolbarIconSize = 24;
     QString m_notmuchConfig;
     QString m_dateFormat;
+    QStringList m_forwardPrefixes;
     QString m_language;
     qreal m_messageZoom = 1.0;
     bool m_completionOnFocus = false;