bug#29080: 25.3; dired-x does not update `shell-command-history'

[Matz, Daniel A. (JSC-EG511)]

> Yes, I think so.  See the comments there.

OK, I see.  When dired-x is loaded, `dired-read-shell-command' calls 
`dired-guess-shell-command' instead of calling `read-shell-command' directly.  
And then`dired-guess-shell-command’ ends up calling `read-shell-command', but 
specifies a different history variable.  And `dired-do-shell-command' calls 
`dired-read-shell-command’, but `dired-smart-shell-command’ does not, but 
instead calls `read-shell-command' directly, using the default history variable.

I ended up just making `dired-shell-command-history' an alias for 
`shell-command-history’.

Thank you for the help.  We can close this issue.