[penberg]

Forks pile up next to the directory: turso.1, turso.2, … and their
hidden bases, with no way to tell which are done with but running
fsdiff on each. This adds two ways to deal with them, keeping no state:

$ fsfork -l
FORK                UPDATED         STATUS
../turso.1          4 days ago      unchanged
../turso.3          1 day ago       9 files only here
../.turso.2.base    2 hours ago     base only
../turso.swebench   9 minutes ago   merged

$ fsfork --prune
removed ../turso.1
removed ../.turso.2.base
fsfork: kept 1 with work only here, 1 recent

fsfork -l [dir]

Lists the forks next to the directory, found by their bases, so that a
directory merely named like one is not listed. For each:

• UPDATED: when a file the fork changed last changed, or when the fork
  was made, if none has. The base's birth time is the directory's on macOS,
  as clonefile keeps it, so it cannot say when the fork was made.
• STATUS:
  • unchanged: as fsdiff would say;
  • merged: the directory has the changes, so removing the fork loses
    nothing. It is merged if the fork's patch undoes in the directory
    (git apply --reverse --check), so it stays merged after the directory
    changes again;
  • N files only here: the changes to N files are only in the fork;
  • base only: the fork was removed without its base.

Those left alone longest come first.

fsfork --prune [dir]

Removes the forks -l lists as unchanged or merged, with their
bases, and bases left over. It keeps:

• those with work only here;
• those changed in the last hour, as one just made may have a command
  starting in it (recent);
• any the working directory is in (in use).

It says each it removed on stdout, and how many it kept, and why, on one
line on stderr. There is no dry run: -l shows what it would remove.

Also

• fsdiff's git module moves into the fsfork library, so that -l
  compares a fork with its base by the same rules fsdiff does.
• Debug builds take FSFORK_TEST_LEFT_ALONE=<secs> in place of the hour,
  as a test cannot make a fork's base older; release builds ignore it.

Not done

• Forks made elsewhere, with a path given, are not listed or pruned.
• An agent reading in an unchanged fork for over an hour, writing nothing,
  would have it pruned under it. Build output, which is ignored, counts only
  if it makes a new directory at the top of the fork.
• -l in a fork lists that fork's forks, not its siblings.

Testing

cargo test: conformance tests for listing (each status, a lookalike
directory, from the parent), for staying merged after the directory moves
on, for pruning (nothing within the hour; then what is removed, what is
kept and why, the working directory's fork kept), and for the options
-l and --prune refuse. Tried on real forks of this repository.