We need to rewrite the loop for gmime-3.0; move the loop body to its
own function to avoid code duplication. Keep the common exit via
"goto DONE" to make this pure code movement. It's important to note
that the existing exit path only deallocates the iterator.
We want to reuse the scanner definition with a different table. This
is mainly code movement, and making the state table part of the filter
struct/class.
Commit d5523ead90 ("Mark some structures in the library interface
with visibility=default attribute.") fixed some mixed visibility
issues with structs. With the symbol default visibility reversed, this
is no longer a problem.
The dynamic generation of the linker version script for libnotmuch
exports has grown rather complicated.
Reverse the visibility control by hiding symbols by default using
-fvisibility=hidden, and explicitly exporting symbols in notmuch.h
using #pragma GCC visibility. (We could also use __attribute__
((visibility ("default"))) for each exported function, but the pragma
is more convenient.)
The above is not quite enough alone, as it would "leak" a number of
weak symbols from Xapian and C++ standard library. Combine it with a
small static version script that filters out everything except the
notmuch_* symbols that we explicitly exposed, and the C++ RTTI
typeinfo symbols for exception handling.
Finally, as the symbol hiding test can no longer look at the generated
symbol table, switch the test to parse the functions from notmuch.h.
Commits 9db2145272 ("lib/gen-version-script.h: add getline and
getdelim to notmuch.sym if needed") and 3242e29e57 ("build: add
canonicalize_file_name to symbols exported from libnotmuch.so")
started exporting compat functions from libnotmuch so that the cli
could use them. But we shouldn't export such functions from the
library. They are not part of our ABI. Instead, the cli should include
its own copies of the compat functions.
From a UI perspective this looks similar to what was already provided
for from, subject, and mid, but the implementation is quite
different. It uses the database's list of terms to construct a term
based query equivalent to the passed regular expression.
The index(3) function has been deprecated in POSIX since 2001 and
removed in 2008, and most code in notmuch already calls strchr(3).
This fixes a compilation error on Android whose libc does not have
index(3).
The non-field processor behaviour is is convert the corresponding
queries into a search for the unprefixed terms. This yields pretty
surprising results so I decided to generate a query that would match
the terms (i.e. none with that prefix) generated for an empty header.
The argument is that if the string passed to the field processor has
no spaces, then the added quotes won't have any benefit except for
disabling wildcards. But disabling wildcards doesn't seem very useful
in the normal Xapian query parser, since they're stripped before
generating terms anyway. It does mean that the query 'from:"foo*"' will
not be precisely equivalent to 'from:foo' as it is for the non
field-processor version.
This function was deprecated in notmuch 0.21. We re-use the name for
a status returning version, and deprecate the _st name. One or two
remaining uses of the (removed) non-status returning version fixed at
the same time
This function was deprecated in notmuch 0.21. We finally remove the
deprecated API, and rename the status returning version to the simpler
name. The status returning is kept as a deprecated alias.
Apparently some systems (MacOS?) have a system library called libutil
and the name conflict causes problems. Since this library is quite
notmuch specific, rename it to something less generic.
The object where pointer to `data` was received was deleted before
it was used in _notmuch_string_list_append().
Relevant Coverity messages follow:
3: extract
Assigning: data = std::__cxx11::string(message->doc.()).c_str(),
which extracts wrapped state from temporary of type std::__cxx11::string.
4: dtor_free
The internal representation of temporary of type std::__cxx11::string
is freed by its destructor.
5: use after free:
Wrapper object use after free (WRAPPER_ESCAPE)
Using internal representation of destroyed object local data.
For reasons not completely understood at this time, gmime (as of
2.6.22) is returning a date before 1900 on bad date input. Since this
confuses some other software, we clamp such dates to 0,
i.e. 1970-01-01.
Remove incorrect skipping to first match from init(), and add explicit
skip_to() and check() methods to work around xapian-core bug (the
check() method will also improve speed when filtering by one of
these).
We filter added exclude at add time, rather than modifying the query by
count search. As noted in the comments, there are several ignored
conditions here.
The main goal is to prepare the way for non-destructive (or at least
less destructive) exclude tag handling. It does this by having a
pre-parsed query available for further processing. This also allows us
to provide slightly more precise error messages.
Fix warning caught by clang:
lib/regexp-fields.cc:41:2: warning: 'delete' applied to a pointer that was allocated
with 'new[]'; did you mean 'delete[]'? [-Wmismatched-new-delete]
delete buffer;
^
[]
lib/regexp-fields.cc:37:17: note: allocated with 'new[]' here
char *buffer = new char[len];
^
mid: is the url scheme suggested by URL 2392. We also plan to
introduce more flexible searches for mid: than are possible with
id: (in order not to break assumptions about the special behaviour of
id:, e.g. identifying at most one message).
the idea is that you can run
% notmuch search subject:/<your-favourite-regexp>/
% notmuch search from:/<your-favourite-regexp>/
or
% notmuch search subject:"your usual phrase search"
% notmuch search from:"usual phrase search"
This feature is only available with recent Xapian, specifically
support for field processors is needed.
It should work with bindings, since it extends the query parser.
This is easy to extend for other value slots, but currently the only
value slots are date, message_id, from, subject, and last_mod. Date is
already searchable; message_id is left for a followup commit.
This was originally written by Austin Clements, and ported to Xapian
field processors (from Austin's custom query parser) by yours truly.
The retries are hardcoded to a small number, and error handling aborts
than propagating errors from notmuch_database_reopen. These are both
somewhat justified by the assumption that most things that can go
wrong in Xapian::Database::reopen are rare and fatal. Here's the brief
discussion with Xapian upstream:
24-02-2017 08:12:57 < bremner> any intuition about how likely
Xapian::Database::reopen is to fail? I'm catching a
DatabaseModifiedError somewhere where handling any further errors is
tricky, and wondering about treating a failed reopen as as "the
impossible happened, stopping"
24-02-2017 16:22:34 < olly> bremner: there should not be much scope for
failure - stuff like out of memory or disk errors, which are probably a
good enough excuse to stop
The two g_hash_table functions (insert, add) have different behaviour
with respect to existing keys. g_hash_table_insert frees the new key,
while g_hash_table_add (which is really g_hash_table_replace in
disguise) frees the existing key. With this change 'ref' is live until
the end of the function (assuming single-threaded access to
'hash'). We can't guarantee it will continue to be live in the
future (i.e. there may be a future key duplication) so we copy it with
the allocation context passed to parse_references (in practice this is
the notmuch_message_t object whose parents we are finding).
Thanks to Tomi for the simpler approach to the problem based on
reading the fine glib manual.
Replace multiple tables with some flags in a single table. This makes
the code in notmuch_database_open_verbose a bit shorter, and it should
also make it easier to add other options to fields, e.g. regexp
searching.
From #xapian
olly> bremner: btw, i noticed notmuch count see ms to request all the documents and then ignores them
bremner> hmm. There's something funny about the way that notmuch uses matches in general iirc
olly> it should be able to do: mset = enquire.get_mset (0, 0, notmuch->xapian_db->get_doccount ());
...
olly> get_matches_estimated() will be exact because check_at_least is the size of the database
We already depend on glib both directly and indirectly (via gmime). We
might as well make use of its facilities. Drop the embedded libsha1
and use glib for sha1 digests.
The todo comment got separated from the status it's related to at
commit 3f32fd8a1c ("Add missing comment for
NOTMUCH_STATUS_READONLY_DATABASE."). Later, commit b65ca8e0ba ("lib:
modify notmuch.h for automatic document generation") moved it, but to
the wrong place. Fix the location.
It seems that no-one tried to compile without Xapian compact support
since March of 2015, since that's when I introduced a syntax error in
that branch of the ifdef.
Given the choice of maintaining this underused branch of code, or
bumping the Xapian dependency to a version from 2011, it seems
reasonable to do the latter.
This should not change the SONAME, and therefore won't change the
dynamic linking behaviour, but it may help some users debug missing
symbols in case their libnotmuch is too old.
This is needed so that when the map is modified during traversal, and
thus unlinked by the database code, the map is not disposed of until the
iterator is done with it.
We want to be able to query the properties directly, like:
notmuch count property:foo=bar
which should return a count of messages where the property with key
"foo" has value equal to "bar".
I believe the current one is misleading, because in my experiments
Xapian did not add : when prefix and term were both upper case. Indeed,
it's hard to see how it could, because prefixes are added at a layer
above Xapian in our code. See _notmuch_message_add_term for an example.
Also try to explain why this is a good idea. As far as I can ascertain,
this is more of an issue for a system trying to work with an unknown set
of prefixes. Since notmuch has a fixed set of prefixes, and we can
hopefully be trusted not to add XGOLD and XGOLDEN as prefixes, it is
harder for problems to arise.
_notmuch_database_log clears the log buffer each time. Rather than
introducing more complicated semantics about for this function, provide
a second function that does not clear the buffer. This is mainly a
convenience function for callers constructing complex or multi-line log
messages.
The changes to query.cc are to make sure that the common code path of
the new function is tested.
This support will be present only if the appropriate version of xapian
is available _and_ the user did not disable the feature when
building. So there really needs to be some way for the user to check.
Xapian 1.3 has introduced the DB_RETRY_LOCK flag (Xapian bug
275). Detect it in configure and optionally use it. With this flag
commands that need the write lock will wait for their turn instead of
aborting when it's not immediately available.
Amended by db: allow disabling in configure
Fix bug reported in id:20160606124522.g2y2eazhhrwjsa4h@flatcap.org
Although the C99 standard 6.10 is a little non-obvious on this point,
the docs for e.g. gcc are unambiguous. And indeed in practice with the
extra space, this code fails
#include <stdio.h>
#define foo (x) (x+1)
int main(int argc, char **argv){
printf("%d\n",foo(1));
}
Many of the external links found in the notmuch source can be resolved
using https instead of http. This changeset addresses as many as i
could find, without touching the e-mail corpus or expected outputs
found in tests.
Cleaned the following whitespace in lib/* files:
lib/index.cc: 1 line: trailing whitespace
lib/database.cc 5 lines: 8 spaces at the beginning of line
lib/notmuch-private.h: 4 lines: 8 spaces at the beginning of line
lib/message.cc: 1 line: trailing whitespace
lib/sha1.c: 1 line: empty lines at the end of file
lib/query.cc: 2 lines: 8 spaces at the beginning of line
lib/gen-version-script.sh: 1 line: trailing whitespace
It's already kindof gross that this is hardcoded in two different
places. We will also need these later in field processors calling back
into the query parser.
Since xapian provides the ability to restrict the iterator to a given
prefix, we expose this ability to the user. Otherwise we mimic the other
iterator interfances in notmuch (e.g. tags.c).
This is a thin wrapper around the Xapian metadata API. The job of this
layer is to keep the config key value pairs from colliding with other
metadata by transparently prefixing the keys, along with the usual glue
to provide a C interface.
The split of _get_config into two functions is to allow returning of the
return value with different memory ownership semantics.
To fully complete the ghost-on-removal-when-shared-thread-exists
proposal, we need to clear all ghost messages when the last active
message is removed from a thread.
Amended by db: Remove the last test of T530, as it no longer makes sense
if we are garbage collecting ghost messages.
There is no need to add a ghost message upon deletion if there are no
other active messages in the thread.
Also, if the message being deleted was a ghost already, we can just go
ahead and delete it.
Publicly we are only exposing the non-ghost documents (of "type"
"mail"). But internally we might want to inspect the ghost messages
as well.
This changeset adds two new private interfaces to queries to recover
information about alternate document types.
implement ghost-on-removal, the solution to T590-thread-breakage.sh
that just adds a ghost message after removing each message.
It leaks information about whether we've ever seen a given message id,
but it's a fairly simple implementation.
Note that _resolve_message_id_to_thread_id already introduces new
message_ids to the database, so i think just searching for a given
message ID may introduce the same metadata leakage.
The code to skip multiple slashes in _notmuch_database_split_path()
skips back one character too much. This is compensated by a +1 in the
length parameter to the strndup() call. Mostly this works fine, but if
the path is to a file under a top level directory with one character
long name, the directory part is mistaken to be part of the file name
(slash == path in code). The returned directory name will be the empty
string and the basename will be the full path, breaking the indexing
logic in notmuch new.
Fix the multiple slash skipping to keep the slash variable pointing at
the last slash, and adjust strndup() accordingly.
The bug was introduced in
commit e890b0cf40
Author: Carl Worth <cworth@cworth.org>
Date: Sat Dec 19 13:20:26 2009 -0800
database: Store the parent ID for each directory document.
just a little over two months after the initial commit in the Notmuch
code history, making this the longest living bug in Notmuch to date.
Some compilers (older than gcc 4.5 and clang 2.9) do support
__attribute__ ((deprecated)) but not
__attribute__ ((deprecated("message"))).
Check if clang version is at least 3.0, or gcc version
is at least 4.5 to define NOTMUCH_DEPRECATED as the
latter variant above. Otherwise define NOTMUCH_DEPRECATED
as the former variant above.
For a bit simpler implementation clang 2.9 is not included
to use the newer variant. It is just one release, and the
older one works fine. Clang 3.0 was released around 2011-11
and gcc 5.1 2015-04-22 (therefore newer macro for gcc 4.5+)
We can't (but currently do) allow upgrades within transactions because
upgrades need their own transactions. We don't want to re-use the
current transaction because bailing out of an upgrade would mean loosing
all previous changes (because our "atomic" transactions don't commit
before hand). This gives us two options:
1. Fail at the beginning of upgrade (tell the user to end the
transaction, upgrade, and start over).
2. Don't allow the user to start the transaction.
I went with the latter because:
1. There is no reason to call `begin_atomic` unless you intend to to
write to the database and anyone intending to write to the database
should upgrade it first.
2. This means that nothing inside an atomic transaction can ever fail
with NOTMUCH_STATUS_UPGRADE_REQUIRED.
Per RFC 2183, the values for Content-Disposition values are not
case-sensitive. While at it, use the gmime function for getting at the
disposition string instead of referencing the field directly.
This fixes "attachment" tagging and filename term generation for
attachments while indexing.
Although I think it's a pretty bad idea to continue using the old API,
this allows both a more gentle transition for clients of the library,
and allows us to break one monolithic change into a series
It doesn't seem likely we can support simple date:<expr> expanding to
date:<expr>..<expr> any time soon. (This can be done with a future
version of Xapian, or with a custom query query parser.) In the mean
time, provide shorthand date:<expr>..! to mean the same. This is
useful, as the expansion takes place before interpetation, and we can
use, for example, date:yesterday..! to match from beginning of
yesterday to end of yesterday.
Idea from Mark Walters <markwalters1009@gmail.com>.
These functions are all just accessors, and it's pretty clear they don't
modify the query struct. This also fixes one warning I created when I
introduced status.c.
This exposes the committed database revision to library users along
with a UUID that can be used to detect when revision numbers are no
longer comparable (e.g., because the database has been replaced).
This adds a new document value that stores the revision of the last
modification to message metadata, where the revision number increases
monotonically with each database commit.
An alternative would be to store the wall-clock time of the last
modification of each message. In principle this is simpler and has
the advantage that any process can determine the current timestamp
without support from libnotmuch. However, even assuming a computer's
clock never goes backward and ignoring clock skew in networked
environments, this has a fatal flaw. Xapian uses (optimistic)
snapshot isolation, which means reads can be concurrent with writes.
Given this, consider the following time line with a write and two read
transactions:
write |-X-A--------------|
read 1 |---B---|
read 2 |---|
The write transaction modifies message X and records the wall-clock
time of the modification at A. The writer hangs around for a while
and later commits its change. Read 1 is concurrent with the write, so
it doesn't see the change to X. It does some query and records the
wall-clock time of its results at B. Transaction read 2 later starts
after the write commits and queries for changes since wall-clock time
B (say the reads are performing an incremental backup). Even though
read 1 could not see the change to X, read 2 is told (correctly) that
X has not changed since B, the time of the last read. In fact, X
changed before wall-clock time A, but the change was not visible until
*after* wall-clock time B, so read 2 misses the change to X.
This is tricky to solve in full-blown snapshot isolation, but because
Xapian serializes writes, we can use a simple, monotonically
increasing database revision number. Furthermore, maintaining this
revision number requires no more IO than a wall-clock time solution
because Xapian already maintains statistics on the upper (and lower)
bound of each value stream.
- Make lib/notmuch.h the canonical location for the library versioning
information.
- Since the release-check should never fail now, remove it to reduce
complexity.
- Make the version numbers in notmuch.h consistent with the (now
deleted) ones in lib/Makefile.local
The CLI (and bindings) code should really be updated to use the new
status-code-returning versions. Here are some warnings to prod us (and
other clients) to do so.
Previously, we updated the database copy of a message on every call to
_notmuch_message_sync, even if nothing had changed. In particular,
this always happens on a thaw, so a freeze/thaw pair with no
modifications between still caused a database update.
We only modify message documents in a handful of places, so keep track
of whether the document has been modified and only sync it when
necessary. This will be particularly important when we add message
revision tracking.
It turns out that on certain systems like FreeBSD, c++filt is not
installed by default. It's basically OK if we fail the build in that
case, but what's really not OK is for the build to continue and
generate bad binaries.
There are many places in the notmuch code where the path is assumed to be absolute. If someone (TM) wants a project, one could remove these assumptions. In the mean time, prevent users from shooting themselves in the foot.
Update test suite mark tests for this error as no longer broken, and
also convert some tests that used relative paths for nonexistent
directories.
The difference with FILE_ERROR is that this is for things that are
wrong with the path before looking at the disk.
Add some 3 tests; two broken as a reminder to actually use this new
code.
You may wonder why _notmuch_message_file_open_ctx has two parameters.
This is because we need sometime to use a ctx which is a
notmuch_message_t. While we could get the database from this, there is
no easy way in C to tell type we are getting.
This is not supposed to change any functionality from an end user
point of view. Note that it will eliminate some output to stderr. The
query debugging output is left as is; it doesn't really fit with the
current primitive logging model. The remaining "bad" fprintf will need
an internal API change.
The compatibility wrapper ensures that clients calling
notmuch_database_open will receive consistent output for now.
The changes to notmuch-{new,search} and test/symbol-test are just to
make the test suite pass.
The use of IGNORE_RESULT is justified by two things. 1) I don't know
what else to do. 2) asprintf guarantees the output string is NULL if
an error occurs, so at least we are not passing garbage back.
The default is actually exact if no checkatleast parameter is
specified. This change makes that explicit, mainly for documentation,
but also to be safe in the unlikely event of a change of default.
[ commit message rewritten by db based on id:87lho0nlkk.fsf@nikula.org
]
The install_name of libnotmuch.dylib on Mac OS X is what is written
into a program that links against it. If it is just the name of the
shared library file, as opposed to the full path, the program won't be
able to find it when it runs and will abort. Instead, the install_name
should be the full path to the shared library (in its final installed
location).
Why does Notmuch work without this patch when installed via Homebrew?
The answer is twofold. One, /usr/local/lib is a special location in
which the dynamic linker will look by default to find shared libraries.
Homebrew highly recommends installing to /usr/local, and, assuming it
has been configured this way, the Notmuch library will end up installed
in /usr/local/lib, and the dynamic linker will find it. Two, Homebrew
globally corrects all install names in dynamically shared libraries and
binaries for each package it installs. So, even if the install names in
a package's binaries and libraries are incorrect, Homebrew corrects them
automatically, and no one ever knows.
Why does Notmuch work without this patch when installed via MacPorts?
The answer is that MacPorts applies a patch just like this patch to fix
the same problem.
This indicates upwardly compatible changes, namely adding new symbols.
Although we don't formally need to do this until the next release,
there is no hard in doing it now, as long as we don't bump the minor
version for every addition between now and the release.
This at least allows distinguishing between out of memory and Xapian
exceptions. Adding finer grained status codes would allow different
Xapian exceptions to be preserved.
Adding wrappers allows people to transition gradually to the new API,
at the cost of bloating the library API a bit.
This adds the indexing support for the "mimetype:" term and removes
the broken test flag. The indexing is probablistic in Xapian terms,
which gives a better experience to end users. Standard content-types
of the form "foo/bar" are automatically interpreted as phrases in
Xapian due to the embedded slash.
Assume, separate messages with application/pdf and application/x-pdf
are indexed, then:
- mimetype:application/x-pdf will find only the application/x-pdf
- mimetype:application/pdf will find only the application/pdf
- mimetype:pdf will find both of the messages
This feature will exist in all newly created databases, but there is
no upgrade provided for it. If this flag exists, it indicates that
the database was created after the indexed MIME-types feature was
added.
_thread_set_subject_from_message sometimes replaces the subject, making the
cur_subject point to free'd memory
==6550== ERROR: AddressSanitizer: heap-use-after-free on address 0x601a0000bec0 at pc 0x4464a4 bp 0x7fffa40be910 sp 0x7fffa40be908
READ of size 1 at 0x601a0000bec0 thread T0
#0 0x4464a3 in _thread_add_matched_message /home/todd/.apps/notmuch/lib/thread.cc:369
#1 0x443c2c in notmuch_threads_get /home/todd/.apps/notmuch/lib/query.cc:496
#2 0x41d947 in do_search_threads /home/todd/.apps/notmuch/notmuch-search.c:131
#3 0x40a3fe in main /home/todd/.apps/notmuch/notmuch.c:345
#4 0x7f4e535b4ec4 in __libc_start_main /build/buildd/eglibc-2.19/csu/libc-start.c:287
#5 0x40abe6 in _start ??:?
0x601a0000bec0 is located 96 bytes inside of 134-byte region [0x601a0000be60,0x601a0000bee6)
freed by thread T0 here:
#0 0x7f4e54e6933a in __interceptor_free ??:?
#1 0x7f4e54482fab in _talloc_free ??:?
previously allocated by thread T0 here:
#0 0x7f4e54e6941a in malloc ??:?
#1 0x7f4e54485b5d in talloc_strdup ??:?
==22884== ERROR: AddressSanitizer: heap-buffer-overflow on address 0x601600008291 at pc 0x7ff6295680e5 bp 0x7fff4ab9aa40 sp 0x7fff4ab9aa08
READ of size 1 at 0x601600008291 thread T0
#0 0x7ff6295680e4 in __interceptor_strcmp ??:?
#1 0x44763b in _thread_add_message /home/todd/.apps/notmuch/lib/thread.cc:255
#2 0x4459e8 in notmuch_threads_get /home/todd/.apps/notmuch/lib/query.cc:496
#3 0x41e2a7 in do_search_threads /home/todd/.apps/notmuch/notmuch-search.c:131
#4 0x40a408 in main /home/todd/.apps/notmuch/notmuch.c:345
#5 0x7ff627cb9ec4 in __libc_start_main /build/buildd/eglibc-2.19/csu/libc-start.c:287
#6 0x40abf3 in _start ??:?
0x601600008291 is located 0 bytes to the right of 97-byte region [0x601600008230,0x601600008291)
allocated by thread T0 here:
#0 0x7ff62956e41a in malloc ??:?
#1 0x7ff628b8ab5d in talloc_strdup ??:?
Currently the thread is named based on either the oldest or newest
matching message (depending on the search order). If this message has
an empty subject, though, the thread will show up with an empty
subject in the search results. (See the thread starting with
`id:1412371140-21051-1-git-send-email-david@tethera.net` for an
example.)
This changes the behavior so it will use a non-empty name for the
thread if possible. We name threads based on (a) non-empty matches for
the query, and (b) the search order. If the search order is
oldest-first (as in the default inbox) it chooses the oldest matching
non-empty message as the subject. If the search order is newest-first
it chooses the newest one.
Tamas Szakaly points out [1] that the bug fixed in 51b073c still
exists in at least one place. This change follows the suggestion of
[2] and creates a block scope temporary std::string to avoid the rules
of iterators temporaries.
[1]: id:20141226113755.GA64154@pamparam
[2]: id:20141226230655.GA41992@pamparam
We generally do not support mbox files, but for historical reasons
we've supported single-message mbox files, with a deprecation
message. We've tried dropping the support altogether, but backed out
of it because we'd need to stop indexing them, while keeping support
for previously indexed files. This would be more complicated than
simply supporting single-message mbox files. Therefore, drop the
deprecation message, and just silently accept single-message mboxes.
Currently, if a From-header is of the form:
"" <address@example.com>
the empty string will be treated as a valid real-name, and the entry
in the search results will be empty.
The new behavior here is that we treat an empty real-name field as if
it were null, so that the email address will be used in the search
results instead.
Signed-off-by: Jesse Rosenthal <jrosenthal@jhu.edu>
Previously, it was necessary to link new messages to children to work
around some (though not all) problems with the old metadata-based
approach to stored thread IDs. With ghost messages, this is no longer
necessary, so don't bother with child linking when ghost messages are
in use.
This updates the thread linking code to use ghost messages instead of
user metadata to link messages into threads.
In contrast with the old approach, this is actually correct.
Previously, thread merging updated only the thread IDs of message
documents, not thread IDs stored in user metadata. As originally
diagnosed by Mark Walters [1] and as demonstrated by the broken
T260-thread-order test, this can cause notmuch to fail to link
messages even though they're in the same thread. In principle the old
approach could have been fixed by updating the user metadata thread
IDs as well, but these are not indexed and hence this would have
required a full scan of all stored thread IDs. Ghost messages solve
this problem naturally by reusing the exact same thread ID and message
ID representation and indexing as regular messages.
Furthermore, thanks to this greater symmetry, ghost messages are also
algorithmically simpler. We continue to support the old user metadata
format, so this patch can't delete any code, but when we do remove
support for the old format, several functions can simply be deleted.
[1] id:8738h7kv2q.fsf@qmul.ac.uk
This updates the message abstraction to support ghost messages: it
adds a message flag that distinguishes regular messages from ghost
messages, and an internal function for initializing a newly created
(blank) message as a ghost message.
