Add thread editing commands.

12 files changed, 312 insertions, 6 deletions

diff --git a/OPS b/OPS
index 0844487f..1db524a8 100644
--- a/OPS
+++ b/OPS
@@ -96,6 +96,7 @@ OP_LAST_ENTRY "move to the last entry"
 OP_LIST_REPLY "reply to specified mailing list"
 OP_MACRO "execute a macro"
 OP_MAIL "compose a new mail message"
+OP_MAIN_BREAK_THREAD "break the thread in two"
 OP_MAIN_CHANGE_FOLDER "open a different folder"
 OP_MAIN_CHANGE_FOLDER_READONLY "open a different folder in read only mode"
 OP_MAIN_CLEAR_FLAG "clear a status flag from a message"
@@ -105,6 +106,7 @@ OP_MAIN_FETCH_MAIL "retrieve mail from POP server"
 OP_MAIN_FIRST_MESSAGE "move to the first message"
 OP_MAIN_LAST_MESSAGE "move to the last message"
 OP_MAIN_LIMIT "show only messages matching a pattern"
+OP_MAIN_LINK_THREADS "link tagged message to the current one"
 OP_MAIN_NEXT_NEW "jump to the next new message"
 OP_MAIN_NEXT_NEW_THEN_UNREAD "jump to the next new or unread message"
 OP_MAIN_NEXT_SUBTHREAD "jump to the next subthread"
diff --git a/copy.c b/copy.c
index d1b3f7c2..60ae50e9 100644
--- a/copy.c
+++ b/copy.c
@@ -99,6 +99,12 @@ mutt_copy_hdr (FILE *in, FILE *out, long off_start, long off_end, int flags,
 	    (ascii_strncasecmp ("Content-Length:", buf, 15) == 0 ||
 	     ascii_strncasecmp ("Lines:", buf, 6) == 0))
 	  continue;
+	if ((flags & CH_UPDATE_REFS) &&
+	    ascii_strncasecmp ("References:", buf, 11) == 0)
+	  continue;
+	if ((flags & CH_UPDATE_IRT) &&
+	    ascii_strncasecmp ("In-Reply-To:", buf, 12) == 0)
+	  continue;
 	ignore = 0;
       }
 
@@ -197,6 +203,12 @@ mutt_copy_hdr (FILE *in, FILE *out, long off_start, long off_end, int flags,
 	     ascii_strncasecmp ("type:", buf + 8, 5) == 0)) ||
 	   ascii_strncasecmp ("mime-version:", buf, 13) == 0))
 	continue;
+      if ((flags & CH_UPDATE_REFS) &&
+	  ascii_strncasecmp ("References:", buf, 11) == 0)
+	continue;
+      if ((flags & CH_UPDATE_IRT) &&
+	  ascii_strncasecmp ("In-Reply-To:", buf, 12) == 0)
+	continue;
 
       /* Find x -- the array entry where this header is to be saved */
       if (flags & CH_REORDER)
@@ -330,6 +342,8 @@ mutt_copy_hdr (FILE *in, FILE *out, long off_start, long off_end, int flags,
  	CH_XMIT		ignore Lines: and Content-Length:
  	CH_WEED		do header weeding
 	CH_NOQFROM      ignore ">From " line
+	CH_UPDATE_IRT	update the In-Reply-To: header
+	CH_UPDATE_REFS	update the References: header
 
    prefix
    	string to use if CH_PREFIX is set
@@ -339,6 +353,9 @@ int
 mutt_copy_header (FILE *in, HEADER *h, FILE *out, int flags, const char *prefix)
 {
   char buffer[SHORT_STRING];
+
+  flags |= (h->irt_changed ? CH_UPDATE_IRT : 0)
+         | (h->refs_changed ? CH_UPDATE_REFS : 0);
   
   if (mutt_copy_hdr (in, out, h->offset, h->content->offset, flags, prefix) == -1)
     return (-1);
@@ -362,7 +379,56 @@ mutt_copy_header (FILE *in, HEADER *h, FILE *out, int flags, const char *prefix)
   if (flags & CH_UPDATE)
   {
     if ((flags & CH_NOSTATUS) == 0)
+#ifdef USE_IMAP
+#define NEW_ENV new_env
+#else
+#define NEW_ENV env
+#endif
     {
+      if (h->irt_changed && h->NEW_ENV->in_reply_to)
+      {
+	LIST *listp = h->NEW_ENV->in_reply_to;
+
+	if (fputs ("In-Reply-To: ", out) == EOF)
+	  return (-1);
+
+	for (; listp; listp = listp->next)
+	  if ((fputs (listp->data, out) == EOF) || (fputc (' ', out) == EOF))
+	    return (-1);
+
+	if (fputc ('\n', out) == EOF)
+	  return (-1);
+      }
+
+      if (h->refs_changed && h->NEW_ENV->references)
+      {
+	LIST *listp = h->NEW_ENV->references, *refs = NULL, *t;
+
+	if (fputs ("References: ", out) == EOF)
+	  return (-1);
+
+	/* Mutt stores references in reverse order, thus we create
+	 * a reordered refs list that we can put in the headers */
+	for (; listp; listp = listp->next, refs = t)
+	{
+	  t = (LIST *)safe_malloc (sizeof (LIST));
+	  t->data = listp->data;
+	  t->next = refs;
+	}
+
+	for (; refs; refs = refs->next)
+	  if ((fputs (refs->data, out) == EOF) || (fputc (' ', out) == EOF))
+	    return (-1);
+
+	/* clearing refs from memory */
+	for (t = refs; refs; refs = t->next, t = refs)
+	  safe_free ((void **)&refs);
+
+	if (fputc ('\n', out) == EOF)
+	  return (-1);
+      }
+#undef NEW_ENV
+
       if (h->old || h->read)
       {
 	if (fputs ("Status: ", out) == EOF)
diff --git a/curs_main.c b/curs_main.c
index c2b7c8c7..1d96c891 100644
--- a/curs_main.c
+++ b/curs_main.c
@@ -936,6 +936,11 @@ CHECK_IMAP_ACL(IMAP_ACL_DELETE);
 	else
 	{
 	  mutt_set_flag (Context, CURHDR, M_TAG, !CURHDR->tagged);
+
+	  Context->last_tag = CURHDR->tagged ? CURHDR :
+	    ((Context->last_tag == CURHDR && !CURHDR->tagged)
+	     ? NULL : Context->last_tag);
+
 	  menu->redraw = REDRAW_STATUS;
 	  if (option (OPTRESOLVE) && menu->current < Context->vcount - 1)
 	  {
@@ -1176,6 +1181,77 @@ CHECK_IMAP_ACL(IMAP_ACL_DELETE);
 	}
 	break;
 
+      case OP_MAIN_BREAK_THREAD:
+
+	CHECK_MSGCOUNT;
+        CHECK_VISIBLE;
+	CHECK_READONLY;
+
+        if ((Sort & SORT_MASK) != SORT_THREADS)
+	  mutt_error _("Threading is not enabled.");
+	else
+	{
+	  {
+	    HEADER *oldcur = CURHDR;
+
+	    mutt_break_thread (CURHDR);
+	    mutt_sort_headers (Context, 1);
+	    menu->current = oldcur->virtual;
+	  }
+
+	  Context->changed = 1;
+	  mutt_message _("Thread broken");
+
+	  if (menu->menu == MENU_PAGER)
+	  {
+	    op = OP_DISPLAY_MESSAGE;
+	    continue;
+	  }
+	  else
+	    menu->redraw |= REDRAW_INDEX;
+	}
+
+	  break;
+
+      case OP_MAIN_LINK_THREADS:
+
+	CHECK_MSGCOUNT;
+        CHECK_VISIBLE;
+	CHECK_READONLY;
+
+        if ((Sort & SORT_MASK) != SORT_THREADS)
+	  mutt_error _("Threading is not enabled.");
+	else if (!CURHDR->env->message_id)
+	  mutt_error _("No Message-ID: header available to link thread");
+	else if (!tag && (!Context->last_tag || !Context->last_tag->tagged))
+	  mutt_error _("First, please tag a message to be linked here");
+	else 
+	{
+	  HEADER *oldcur = CURHDR;
+
+	  if (mutt_link_threads (CURHDR, tag ? NULL : Context->last_tag,
+				 Context))
+	  {
+	    mutt_sort_headers (Context, 1);
+	    menu->current = oldcur->virtual;
+	    
+	    Context->changed = 1;
+	    mutt_message _("Threads linked");
+	  }
+	  else
+	    mutt_error _("No thread linked");
+	}
+
+	if (menu->menu == MENU_PAGER)
+	{
+	  op = OP_DISPLAY_MESSAGE;
+	  continue;
+	}
+	else
+	  menu->redraw |= REDRAW_STATUS | REDRAW_INDEX;
+
+	break;
+
       case OP_EDIT_TYPE:
 
 	CHECK_MSGCOUNT;
diff --git a/doc/manual.sgml.head b/doc/manual.sgml.head
index 87be7dc1..4c0ebcc5 100644
--- a/doc/manual.sgml.head
+++ b/doc/manual.sgml.head
@@ -2334,8 +2334,43 @@ used a threaded news client, this is the same concept.  It makes dealing
 with large volume mailing lists easier because you can easily delete
 uninteresting threads and quickly find topics of value.
 
+<sect1>Editing threads
+<p>
+Mutt has the ability to dynamically restructure threads that are broken
+either by misconfigured software or bad behaviour from some
+correspondents. This allows to clean your mailboxes formats) from these
+annoyances which make it hard to follow a discussion.
+
+If you want to use these functions with IMAP, you need to compile Mutt
+with the <em/--enable-imap-edit-threads/ configure flag.
+
+<sect2>Linking threads
+<p>
+
+Some mailers tend to "forget" to correctly set the "In-Reply-To:" and
+"References:" headers when replying to a message. This results in broken
+discussions because Mutt has not enough information to guess the correct
+threading.
+You can fix this by tagging the reply, then moving to the parent message
+and using the ``link-threads'' function (bound to & by default). The
+reply will then be connected to this "parent" message.
+
+You can also connect multiple childs at once, tagging them and using the
+tag-prefix command (';') or the auto_tag option.
+
+<sect2>Breaking threads
+<p>
+
+On mailing lists, some people are in the bad habit of starting a new
+discussion by hitting "reply" to any message from the list and changing
+the subject to a totally unrelated one.
+You can fix such threads by using the ``break-thread'' function (bound
+by default to #), which will turn the subthread starting from the
+current message into a whole different thread.
+
 <sect1>Delivery Status Notification (DSN) Support
 <p>
+
 RFC1894 defines a set of MIME content types for relaying information
 about the status of electronic mail messages.  These can be thought of as
 ``return receipts.'' Berkeley sendmail 8.8.x currently has some command
diff --git a/functions.h b/functions.h
index 47181cc7..6e1be51a 100644
--- a/functions.h
+++ b/functions.h
@@ -69,6 +69,7 @@ struct binding_t OpGeneric[] = {
 struct binding_t OpMain[] = {
   { "create-alias",		OP_CREATE_ALIAS,		"a" },
   { "bounce-message",		OP_BOUNCE_MESSAGE,		"b" },
+  { "break-thread",		OP_MAIN_BREAK_THREAD,		"#" },
   { "change-folder",		OP_MAIN_CHANGE_FOLDER,		"c" },
   { "change-folder-readonly",	OP_MAIN_CHANGE_FOLDER_READONLY,	"\033c" },
   { "collapse-thread",		OP_MAIN_COLLAPSE_THREAD,	"\033v" },
@@ -95,6 +96,7 @@ struct binding_t OpMain[] = {
   { "next-undeleted",		OP_MAIN_NEXT_UNDELETED,		"j" },
   { "previous-undeleted",	OP_MAIN_PREV_UNDELETED,		"k" },
   { "limit",			OP_MAIN_LIMIT,			"l" },
+  { "link-threads",		OP_MAIN_LINK_THREADS,		"&" },
   { "list-reply",		OP_LIST_REPLY,			"L" },
   { "mail",			OP_MAIL,			"m" },
   { "toggle-new",		OP_TOGGLE_NEW,			"N" },
@@ -153,6 +155,7 @@ struct binding_t OpMain[] = {
 };
 
 struct binding_t OpPager[] = {
+  { "break-thread",	OP_MAIN_BREAK_THREAD,		"#" },
   { "create-alias",	OP_CREATE_ALIAS,		"a" },
   { "bounce-message",	OP_BOUNCE_MESSAGE,		"b" },
   { "change-folder",	OP_MAIN_CHANGE_FOLDER,		"c" },
@@ -175,6 +178,7 @@ struct binding_t OpPager[] = {
   { "next-entry",	OP_NEXT_ENTRY,			"J" },
   { "previous-undeleted",OP_MAIN_PREV_UNDELETED,	"k" },
   { "previous-entry",	OP_PREV_ENTRY,			"K" },
+  { "link-threads",	OP_MAIN_LINK_THREADS,		"&" },
   { "list-reply",	OP_LIST_REPLY,			"L" },
   { "redraw-screen",	OP_REDRAW,			"\014" },
   { "mail",		OP_MAIL,			"m" },
diff --git a/imap/imap.c b/imap/imap.c
index 59560c21..7bcd8f09 100644
--- a/imap/imap.c
+++ b/imap/imap.c
@@ -1065,9 +1065,11 @@ int imap_sync_mailbox (CONTEXT* ctx, int expunge, int* index_hint)
       mutt_message (_("Saving message status flags... [%d/%d]"), n+1,
         ctx->msgcount);
 
-      /* if attachments have been deleted we delete the message and reupload
-       * it. This works better if we're expunging, of course. */
-      if (ctx->hdrs[n]->attach_del)
+      /* if the message has been rethreaded or attachments have been deleted
+       * we delete the message and reupload it.
+       * This works better if we're expunging, of course. */
+      if (ctx->hdrs[n]->refs_changed || ctx->hdrs[n]->irt_changed ||
+	  ctx->hdrs[n]->attach_del)
       {
 	dprint (3, (debugfile, "imap_sync_mailbox: Attachments to be deleted, falling back to _mutt_save_message\n"));
 	if (!appendctx)
diff --git a/mh.c b/mh.c
index eff55bd4..2c1c6343 100644
--- a/mh.c
+++ b/mh.c
@@ -1382,7 +1382,7 @@ static int mh_sync_message (CONTEXT * ctx, int msgno)
 {
   HEADER *h = ctx->hdrs[msgno];
 
-  if (h->attach_del)
+  if (h->attach_del || h->refs_changed || h->irt_changed)
     if (mh_rewrite_message (ctx, msgno) != 0)
       return -1;
 
@@ -1393,9 +1393,9 @@ static int maildir_sync_message (CONTEXT * ctx, int msgno)
 {
   HEADER *h = ctx->hdrs[msgno];
 
-  if (h->attach_del)
+  if (h->attach_del || h->refs_changed || h->irt_changed)
   {
-    /* when doing attachment deletion, fall back to the MH case. */
+    /* when doing attachment deletion/rethreading, fall back to the MH case. */
     if (mh_rewrite_message (ctx, msgno) != 0)
       return (-1);
   }
diff --git a/mutt.h b/mutt.h
index 86e31623..03ec618e 100644
--- a/mutt.h
+++ b/mutt.h
@@ -94,6 +94,8 @@
 #define CH_WEED_DELIVERED (1<<13) /* weed eventual Delivered-To headers */
 #define CH_FORCE_FROM	(1<<14)	/* give CH_FROM precedence over CH_WEED? */
 #define CH_NOQFROM	(1<<15)	/* give CH_FROM precedence over CH_WEED? */
+#define CH_UPDATE_IRT	(1<<16) /* update In-Reply-To: */
+#define CH_UPDATE_REFS	(1<<17) /* update References: */
 
 /* flags for mutt_enter_string() */
 #define  M_ALIAS   1      /* do alias "completion" by calling up the alias-menu */
@@ -551,6 +553,7 @@ typedef struct spam_list_t
 void mutt_free_list (LIST **);
 void mutt_free_rx_list (RX_LIST **);
 void mutt_free_spam_list (SPAM_LIST **);
+LIST *mutt_copy_list (LIST *);
 int mutt_matches_ignore (const char *, LIST *);
 
 /* add an element to a list */
@@ -706,6 +709,8 @@ typedef struct header
   unsigned int subject_changed : 1; 	/* used for threading */
   unsigned int threaded : 1;	    	/* used for threading */
   unsigned int display_subject : 1; 	/* used for threading */
+  unsigned int irt_changed : 1; /* In-Reply-To changed to link/break threads */
+  unsigned int refs_changed : 1; /* References changed to break thread */
   unsigned int recip_valid : 1;  	/* is_recipient is valid */
   unsigned int active : 1;	    	/* message is not to be removed */
   unsigned int trash : 1;		/* message is marked as trashed on disk.
@@ -746,6 +751,10 @@ typedef struct header
   char *tree;           	/* character string to print thread tree */
   struct thread *thread;
 
+#ifdef USE_IMAP
+  ENVELOPE *new_env;	/* envelope information for rethreading */
+#endif
+
 #ifdef MIXMASTER
   LIST *chain;
 #endif
@@ -810,6 +819,7 @@ typedef struct
   char *pattern;                /* limit pattern string */
   pattern_t *limit_pattern;     /* compiled limit pattern */
   HEADER **hdrs;
+  HEADER *last_tag;		/* last tagged msg. used to link threads */
   THREAD *tree;			/* top of thread tree */
   HASH *id_hash;		/* hash table by msg id */
   HASH *subj_hash;		/* hash table by subject */
diff --git a/mx.c b/mx.c
index d27a775c..0c1b2ac5 100644
--- a/mx.c
+++ b/mx.c
@@ -1165,6 +1165,8 @@ int mx_sync_mailbox (CONTEXT *ctx, int *index_hint)
         ctx->deleted = 0;
       }
     }
+    else if (ctx->last_tag && ctx->last_tag->deleted)
+      ctx->last_tag = NULL; /* reset last tagged msg now useless */
   }
 
   /* really only for IMAP - imap_sync_mailbox results in a call to
diff --git a/pager.c b/pager.c
index b558431a..6796166f 100644
--- a/pager.c
+++ b/pager.c
@@ -2498,6 +2498,11 @@ CHECK_IMAP_ACL(IMAP_ACL_WRITE);
       case OP_TAG:
 	CHECK_MODE(IsHeader (extra));
 	mutt_set_flag (Context, extra->hdr, M_TAG, !extra->hdr->tagged);
+
+	Context->last_tag = extra->hdr->tagged ? extra->hdr :
+	  ((Context->last_tag == extra->hdr && !extra->hdr->tagged)
+	   ? NULL : Context->last_tag);
+
 	redraw = REDRAW_STATUS | REDRAW_INDEX;
 	if (option (OPTRESOLVE))
 	{
diff --git a/protos.h b/protos.h
index 248002b8..5dcb7273 100644
--- a/protos.h
+++ b/protos.h
@@ -165,6 +165,7 @@ void mutt_block_signals (void);
 void mutt_block_signals_system (void);
 void mutt_body_handler (BODY *, STATE *);
 int  mutt_bounce_message (FILE *fp, HEADER *, ADDRESS *);
+void mutt_break_thread (HEADER *);
 void mutt_buffy (char *, size_t);
 int  mutt_buffy_list (void);
 void mutt_canonical_charset (char *, size_t, const char *);
@@ -307,6 +308,7 @@ int mutt_is_list_recipient (int, ADDRESS *, ADDRESS *);
 int mutt_is_subscribed_list (ADDRESS *);
 int mutt_is_text_part (BODY *);
 int mutt_is_valid_mailbox (const char *);
+int mutt_link_threads (HEADER *, HEADER *, CONTEXT *);
 int mutt_lookup_mime_type (BODY *, const char *);
 int mutt_match_rx_list (const char *, RX_LIST *);
 int mutt_match_spam_list (const char *, SPAM_LIST *, char *, int);
diff --git a/thread.c b/thread.c
index 28626651..4c8fe101 100644
--- a/thread.c
+++ b/thread.c
@@ -1344,3 +1344,105 @@ HASH *mutt_make_subj_hash (CONTEXT *ctx)
 
   return hash;
 }
+
+static void clean_references (THREAD *brk, THREAD *cur)
+{
+  THREAD *p;
+  LIST *ref = NULL;
+  int done = 0;
+
+  for (; cur; cur = cur->next, done = 0)
+  {
+    /* parse subthread recursively */
+    clean_references (brk, cur->child);
+
+    if (!cur->message)
+      break; /* skip pseudo-message */
+
+    /* Looking for the first bad reference according to the new threading.
+     * Optimal since Mutt stores the references in reverse order, and the
+     * first loop should match immediatly for mails respecting RFC2822. */
+    for (p = brk; !done && p; p = p->parent)
+      for (ref = cur->message->env->references; p->message && ref; ref = ref->next)
+	if (!mutt_strcasecmp (ref->data, p->message->env->message_id))
+	{
+	  done = 1;
+	  break;
+	}
+
+    if (done)
+    {
+      HEADER *h = cur->message;
+
+      /* clearing the References: header from obsolete Message-Id(s) */
+      mutt_free_list (&ref->next);
+
+#ifdef USE_IMAP
+      if (h->new_env)
+	mutt_free_list (&h->new_env->references);
+      else
+	h->new_env = mutt_new_envelope ();
+
+      h->new_env->references = mutt_copy_list (h->env->references);
+#endif
+
+      h->refs_changed = h->changed = 1;
+    }
+  }
+}
+
+void mutt_break_thread (HEADER *hdr)
+{
+  mutt_free_list (&hdr->env->in_reply_to);
+  mutt_free_list (&hdr->env->references);
+  hdr->irt_changed = hdr->refs_changed = hdr->changed = 1;
+
+#ifdef USE_IMAP
+  if (hdr->new_env)
+  {
+    mutt_free_list (&hdr->new_env->in_reply_to);
+    mutt_free_list (&hdr->new_env->references);
+  }
+  else
+    hdr->new_env = mutt_new_envelope ();
+#endif
+
+  clean_references (hdr->thread, hdr->thread->child);
+}
+
+static int link_threads (HEADER *parent, HEADER *child, CONTEXT *ctx)
+{
+  if (child == parent)
+    return 0;
+
+  mutt_break_thread (child);
+
+  child->env->in_reply_to = mutt_new_list ();
+  child->env->in_reply_to->data = safe_strdup (parent->env->message_id);
+
+#ifdef USE_IMAP
+  child->new_env->in_reply_to = mutt_new_list ();
+  child->new_env->in_reply_to->data = safe_strdup (parent->env->message_id);
+#endif
+  
+  mutt_set_flag (ctx, child, M_TAG, 0);
+  
+  child->irt_changed = child->changed = 1;
+  return 1;
+}
+
+int mutt_link_threads (HEADER *cur, HEADER *last, CONTEXT *ctx)
+{
+  int i, changed = 0;
+
+  if (!last)
+  {
+    for (i = 0; i < ctx->vcount; i++)
+      if (ctx->hdrs[Context->v2r[i]]->tagged)
+	changed |= link_threads (cur, ctx->hdrs[Context->v2r[i]], ctx);
+  }
+  else
+    changed = link_threads (cur, last, ctx);
+
+  return changed;
+}