Retrieves the fully resolved path to the currently executing fish binary
(regardless of PATH). Can be used to ensure that the same fish is
launched again from a script.
`get_executable_path()` moved from fish binary to libfish, also cleaned
up some duplicated (but differing!) definitions of PATH_MAX (which was
used by that function) in the process.
This teaches the status command to work with features.
'status features' will show a table listing all known features and whether
they are currently on or off.
`status test-feature` will test an individual feature, setting the exit status to
0 if the feature is on, 1 if off, 2 if unknown.
As part of addressing #1310 I decided it makes more sense to replace
`current-function` with just `function`, etc., because I'm going to add
flags to let the user specify which stack level they are interested in.
With the default being zero or the "current" level.
This implements `status is-breakpoint` that returns true if the current
shell prompt is displayed in the context of a `breakpoint` command.
This also fixes several bugs. Most notably making `breakpoint` a no-op if
the shell isn't interactive. Also, typing `breakpoint` at an interactive
prompt should be an error rather than creating a new nested debugging
context.
Partial fix for #1310
Running the tests on travis revealed that some compilers (or at least
with some options) call the wrong struct constructor if there is more
than one struct with the same name but differing definitions.
