I'm not sure about the filter format...
There are two independent filters: "state" and "assignee". The "state"
filter defaults to including issues whose state is InProgress, Blocked,
Backlog, or New. The "assignee" filter defaults to including all issues,
assigned or not.
The two filters can be independently overridden by the `ent list
FILTER` command. FILTER is a string containing chunks separated by
":", like the PATH environment variable. Each chunk is of the form
"name=value[,value...]". "name" can be either "state" or "assignee".
The "value" arguments to the "state" filter must be one of the valid
states, or it's a parse error.
The "value" arguments to the "assignee" filter are used to
string-compare against the issues "assignee" field, exact matches are
accepted and everything else is rejected. A special assignee filter of
the empty string matches issues that don't have an assignee.
Some examples:
* `ent list` shows issues in the states listed above, and don't filter
based on assignee at all.
* `ent list assignee=seb` shows issues in the states listed above,
but only if the assignee is "seb".
* `ent list assignee=seb,` shows issues in the states listed above,
but only if the assignee is "seb" or if there is no assignee.
* `ent list state=done` shows all issues in the Done state.
* `ent list state=done:assignee=seb` shows issues in the Done state that
are assigned to "seb".
This mostly provides an abstraction for "ephemeral worktrees", which
is a branch checked out in a worktree, to be read and maybe modified,
and the worktree is deleted/pruned when we're done with it.
There are also some helper functions for doing git things, the most
important one creates an orphaned branch.
The intent is to keep all the issues in a git branch. When we want to
do anything with issues (list them, add new issues, modify an issue,
etc) we check the issues branch out into an ephemeral worktree, modify
the branch, and delete the worktree.
