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, 32 insertions, 0 deletions

diff --git a/src/config.cpp b/src/config.cpp
index d91259a..8b784ba 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -170,6 +170,13 @@ QString Account::inboxQuery() const
     return folderQuery(maildir, inboxFolder());
 }
 
+QString Config::generatorTagFor(const QString &generator)
+{
+    // Delegates to the file-local table rather than repeating it, so the
+    // question "which tag does this filter match" has one answer.
+    return generatorTag(generator);
+}
+
 QString Config::allSentQuery() const
 {
     return joinAccountQueries(m_accounts, &Account::sentQuery);
@@ -338,6 +345,31 @@ void Config::load(const QString &path)
         }
     }
 
+    // Extra subject prefixes that mark a message someone forwarded TO the
+    // user, added to the built-in table in composecontext.cpp rather than
+    // replacing it: the built-ins are the spellings that repo already
+    // measured, and a user adding Dutch should not have to restate English.
+    //
+    // Bare words, no colon. The predicate ignores anything else, so a
+    // malformed entry costs that entry and not the whole key.
+    const QStringList forwardPrefixes =
+        settings.value(QStringLiteral("forward_prefixes"))
+            .toStringList();
+    for (const QString &prefix : forwardPrefixes) {
+        const QString trimmed = prefix.trimmed();
+        if (trimmed.isEmpty())
+            continue;
+        // Warned rather than dropped silently: the user asked for something
+        // and is not getting it, the same reason message_zoom warns.
+        if (trimmed.contains(QLatin1Char(':'))) {
+            addProblem(tr("Forward prefix '%1' should be written without "
+                          "its colon; ignoring it.")
+                           .arg(trimmed));
+            continue;
+        }
+        m_forwardPrefixes << trimmed;
+    }
+
     // Absent is silent, the default being 2000. Present but unparseable warns,
     // for the same reason message_zoom does: the user asked for something and
     // is not getting it.