Make b command more useful

[rjkroege]

Per #236, the sam b command requires a full filename path. This can be a lot of typing (or cutting and pasting). b would be easier to use if it permitted autocomplete or (much easier) a regexp match against the currently open files.

[rjkroege]

Note: necessary changes probably go in ecmd.go:/func.*tofile and ecmd.go:/func.*alltofile.

[paul-lalonde]

Is a regexp the right way? Sam (but not acme it seems, having just tried it) allows a redirection to satisfy this, so you can use the shell to glob: b <ls a*.c
If we use a regexp we lose the ability to name files with regexp parts in the name.

[rjkroege]

This:

If we use a regexp we lose the ability to name files with regexp
parts in the name.

seems a quibble 😀 but this

Is a regexp the right way? Sam (but not acme it seems, having just tried
it) allows a redirection to satisfy this, so you can use the shell to glob:
b <ls a*.c

is an excellent point. I should have read the sam manual page before naïvely suggesting adding a regexp to the b command. Let's make it more like sam. Per man:

* b file-list
	Set the current file to the first file named in the list that sam
	also has in its menu.  The list may be expressed <Plan 9 command
 	in which case the file names are taken as words (in the shell
	sense) generated by the Plan 9 command.

I think that we can make the following clarifying assumptions:

• the working directory for the invoked command is the one associated with the Window within which the b command executed
• similarly for relative path arguments to b (this makes autocomplete work)
• the "menu" is the set of currently open Edwood files

[camsn0w]

Is a regexp the right way? Sam (but not acme it seems, having just tried it) allows a redirection to satisfy this, so you can use the shell to glob: b <ls a*.c If we use a regexp we lose the ability to name files with regexp parts in the name.

Following Robert's instruction, I'll be adding tests and getting #418 in so that we've got a b command that does something. Afterwards I'll circle back and get into adding support for autocorrect. Also, there is a way to keep it working with filenames that include regex characters by not doing a regex search when the argument is a absolute path (begins with /), and I'll add this to the PR.
Thank you for the feedback Paul.