Add unit tests and documentation for Eshell pattern-based globs

* lisp/eshell/em-glob.el (eshell-extended-glob): Fix docstring.
(eshell-glob-entries): Refer to '**/' in error (technically, '**' can
end a glob, but it means the same thing as '*').  (Bug#54470)

* test/lisp/eshell/em-glob-tests.el: New file.

* doc/misc/eshell.texi (Globbing): Document pattern-based globs.

1 files changed, 6 insertions, 8 deletions

diff --git a/lisp/eshell/em-glob.el b/lisp/eshell/em-glob.el
index 842f27a4920..52531ff8939 100644
--- a/lisp/eshell/em-glob.el
+++ b/lisp/eshell/em-glob.el
@@ -233,7 +233,10 @@ resulting regular expression."
             "\\'")))
 
 (defun eshell-extended-glob (glob)
-  "Return a list of files generated from GLOB, perhaps looking for DIRS-ONLY.
+  "Return a list of files matched by GLOB.
+If no files match, signal an error (if `eshell-error-if-no-glob'
+is non-nil), or otherwise return GLOB itself.
+
 This function almost fully supports zsh style filename generation
 syntax.  Things that are not supported are:
 
@@ -243,12 +246,7 @@ syntax.  Things that are not supported are:
    foo~x(a|b)  (a|b) will be interpreted as a predicate/modifier list
 
 Mainly they are not supported because file matching is done with Emacs
-regular expressions, and these cannot support the above constructs.
-
-If this routine fails, it returns nil.  Otherwise, it returns a list
-the form:
-
-   (INCLUDE-REGEXP EXCLUDE-REGEXP (PRED-FUNC-LIST) (MOD-FUNC-LIST))"
+regular expressions, and these cannot support the above constructs."
   (let ((paths (eshell-split-path glob))
         eshell-glob-matches message-shown)
     (unwind-protect
@@ -287,7 +285,7 @@ the form:
                    glob (car globs)
                    len (length glob)))))
     (if (and recurse-p (not glob))
-        (error "`**' cannot end a globbing pattern"))
+        (error "`**/' cannot end a globbing pattern"))
     (let ((index 1))
       (setq incl glob)
       (while (and (eq incl glob)