- **Unversioned files** should be trivial to do.

- Maybe pending-moderation support (tickets, ticket comments, wiki edits), depending on how centrally-managed such data need to be (i.e. whether it can be delegated to an app layer).

## Checkin

The SQL code related to checkins has diverged significantly from fossil since libf's checkin support was first implemented (the better part of a decade ago). Though libf's is known to work for the cases supported by its existing feature set, it "really couldn't hurt" to audit the checkin algorithm against fossil's. It's okay if they differ, so long as the results are the same. This will be especially important as merge support is added, since the libf checkin code has never dealt with that. What brings all this up is a corner-case discrepancy discovered in fossil's checkin support regarding merged-and-edited files:
The SQL code related to checkins has diverged significantly from fossil since libf's checkin support was first implemented (the better part of a decade ago). Though libf's is known to work for the cases supported by its existing feature set, it "really couldn't hurt" to audit the checkin algorithm against fossil's. It's okay if they differ, so long as the results are the same. What brings all this up is a corner-case discrepancy discovered in fossil's checkin support regarding merged-and-edited files:

<https://fossil-scm.org/forum/forumpost/03f6b307f89c990b?t=h>

for which Richard proposes a patch to fossil's `checkin.c`:

```
--- src/checkin.c

   }
   db_finalize(&q);
   if( nConflict && !allowConflict ){
     fossil_fatal("abort due to unresolved merge conflicts; "
                  "use --allow-conflict to override");
```

The corresponding code in libf looks *much* different than that now, and it's not currently (2021-09-17) clear whether or how that change would need to apply to libf's impl
The corresponding code in libf looks *much* different than that now, and it's not currently (2021-09-17) clear whether or how that change would need to apply to libf's impl.


# Security-relevant

But not otherwise SCM-relevant...

- **Port over `db_unprotect()` and `db_protect_pop()`** APIs, which allow a db to effectively be made read-only except for limited windows where specific sections of it needs to be writable. Related: `db.c:db_top_autorizer()`.
- **Port over `db_unprotect()` and `db_protect_pop()`** APIs, which allow a db to effectively be made read-only except for limited windows where specific sections of it needs to be writable. Related: `db.c:db_top_authorizer()`.

- ***SQLite3 Security Encryption Extension (SEE)*** support: <https://sqlite.org/see>. We have received an SEE license which can be used to develop this support, so it's now just a matter of figuring out how best to integrate it in such a way that arbitrary clients can plug into it.


# Non-SCM TODOs

In no particular order...

- **Add [SPDX-style](https://spdx.dev/) license attribution** to all source files. This is ongoing.

- **Header file restructuring.** The current separation of the APIs into many `include/fossil-scm/*.h` files is somewhat confusing. The initial intent was to keep my low-end development system of the time from choking on syntax highlighting on one large file, but those days are largely behind me. It may make sense to combine those into 1 public API file, 1 internal API file, and the auto-generated config file(s). (Even then, it's big enough to choke emacs' syntax highlighting on lower-end systems like Raspberry Pi SBCs.)

- **Stop using char as booleans**. This tree historically uses `char` type for booleans. Now that the tree is C99, we can switch to the `bool` type. This is ongoing.

- **f-vdiff**: port in [](fossil:3504672187af59f0) in order to be able to select the diff width based on the terminal size.

- **f-vdiff**/dibu: port the DELETE/INSERT collapsing from [](8752aca1b7187d39) into the ncurses unified diff view.

# Maybe (and Maybe Not) TODO

- **Undo** support.

- **Bring some of the configuration-related state up to date.** The infrastructure is there but the exact list of fossil-supported properties is lagging behind by several years. On the other hand, the majority of such config state is really application-specific and probably has no business being handled by this library. Some settings, e.g. `forbid-delta-manifests`, we internally honor to avoid Grief in downstream repositories. Others, such as the various globs settings, have API-level support and can be honored by the appropriate library APIs via toggles (e.g. the file-add API optionally honors the `ignore-glob` setting).

- **BOMs**. Fossil's diff APIs internally convert their inputs to UTF8 and strip the BOM (if any) from them. libf does not do that. On the one hand i'm hesitant to do so because these blobs can be anything at all (not necessarily SCM controlled). On other other, for annotate's sake it might make sense to do so automatically because the user is passing in artifact IDs instead of file content. On the other other hand, the fossil routine for doing that (blob_to_utf8_no_bom()) is far, far more involved that simply stripping a BOM. i'm torn on whether that's the library's job or not, and really dislike having to either mutate the original inputs or reallocate them to make that conversion. OTOH, fossil does so.

- **Symlinks**. i have always strongly disagreed with the addition of symlink support into fossil: platform-specific constructs simply have no place in the core of any SCM (with the "effectively necessary," as well as unobtrusive, exception of the executable bit). For platforms which don't support symlinks, fossil stores/manages them as plain text files with a single line holding the name of the referenced file. This is *very likely* the only route the library will take to supporting symlinks, especially since the hassles symlink handling caused fossil in late 2020 (long story). Probably the only way the library will support proper symlinks is if someone who uses that feature adds and maintains it.

- **Backlinks**. Crosslinking "should" update the internal list of backlinks from certain text fields, but doing so requires parsing wiki/markdown-format text. See [`backlink.c` in the fossil tree](https://fossil-scm.org/home/file?name=src/backlink.c&ci=trunk) for the details. On the other hand, backlinks support only requires parsing wiki links, not the full grammar, so it might not be as painful as it initially sounds... though somewhat more for markdown, where we're required to do a multi-pass scan to handle its linking model. (We'd also need to handle verbatim blocks to avoid parsing links inside those blocks.)

- **Ticket support**. Ticket handling is surprisingly complicated, due largely to the customizability of the ticket database schema. If fossil-compatible ticket supports gets added to libfossil, it will very likely be because someone other than myself adds it! The core artifact data structure supports tickets, so the bits required for adding it are in place.
- **Ticket support**. Ticket handling is surprisingly complicated, due largely to the customizability of the ticket database schema. If fossil-compatible ticket supports gets added to libfossil, it will very likely be because someone other than myself adds it! The core artifact data structure supports tickets, so the bits required for adding it are in place. Fossil, however, also uses the TH1 scripting engine in its ticket handling and that's an aspect the library-level API should arguably avoid.


# Optimizations

- **Artifact parsing,** in particular of checkins, is *much* slower in libfossil than fossil. Some of this is easily attributable to more abstraction layers, but certainly not all of it. Some optimization of crosslinking speed is certainly in order. As a point of comparison, try `fossil rebuild` vs `f-parseparty --crosslink`. libf parses non-checkin types "plenty fast," e.g. 1600-odd control artifacts in roughly 6ms on my main computer. Checkins, however: <s>6m20s for 15504</s> 2m59s (debug) or 2m30s (non-debug) for 15504 checkins in the main fossil repo, as of this writing (just parsing, without crosslinking). On the sqlite3 repo it can only parse <s>approx. 3000 checkins in 10 minutes, at which point that test got cancelled</s> 24657 checkins in 10m9s (debug? Non-debug?). The reason for the serious speed degradation as the repo size increases is unclear.
  - This is at least partially (roughly 20-33%, based on basic tests) due to libfossil building in debug mode by default.
  - <s>On 2021-03-24 the crosslinking was sped up by roughly 50% via the addition of a content cache identical to fossil's, but it still takes roughly 4m45s to parse and crosslink 16287 checkins in fossil's core repo with a debug libfossil build. 2m30s of that time is parsing.</s>

- In order to support near-arbitrary applications the wiki parsers need to be implemented in such a way that clients can customize (via hooks/callbacks) how links/references are generated.

- The venerable Fossil Wiki format has the lowest priority. In practice markdown has easily taken the lead, and only old (pre-markdown) docs tend to be maintained in that format.


# Non-TODOs

- **Any and all UI-related elements**, including HTML, CSS, and JavaScript. The library will enable such applications but will not provide, e.g., an HTML framework beyond *perhaps* (maybe) wiki rendering.
- **Any and all UI-related elements**, including HTML, CSS, and JavaScript. The library will enable such applications but will not provide, e.g., an HTML framework beyond *perhaps* (maybe) diff and/or wiki rendering (the former being likely but the latter unlikely).

- **Scripting of tickets**. There are no current plans to 100% mimic fossil's th1 scripting of tickets. Fossil's use of TH1 was one of convenience, not long-term practicality. The library itself will have no "official" scripting language, but is designed specifically to make tying it to scripting engines relatively straightforward. We have a standalone copy of TH1 which "could" be integrated with little work, but doing so would not be an ideal path to go down.
- **Scripting of tickets**. There are no current plans to 100% mimic fossil's TH1 scripting of tickets. Fossil's use of TH1 was one of convenience, not long-term practicality. The library itself will have no "official" scripting language, but is designed specifically to make tying it to scripting engines relatively straightforward. We have a standalone copy of TH1 which "could" be integrated with little work, but doing so would not be an ideal path to go down.