tool_urlglob: add named globs

Idea-by: Bastian Jesuiter

Verified by test 2408 - 2411

Closes #21409

docs/cmdline-opts/_GLOBBING.md

@@ -39,4 +39,17 @@ probably have to put the full URL within double quotes to avoid the shell from
 interfering with it. This also goes for other characters treated special, like
 for example '&', '?' and '*'.
 
+The separate globbing components can be referenced in the --output option to
+allow pieces to be reused in the target filename.
+
+Starting in curl 8.21.0, the separate globbing parts can be named and
+referenced by their names. The case sensitive alphanumeric name is set
+enclosed within angle brackets after the opening character. Examples:
+
+    https://fun.example/{<number>one,two,three}.jpg
+
+    ftp://ftp.example.com/file[<range>1-100].txt
+
+Setting the same glob name twice is an error.
+
 Switch off globbing with --globoff.

docs/cmdline-opts/output.md

@@ -69,3 +69,14 @@ override curl's internal binary output in terminal prevention:
 
 Note that the binary output may be caused by the response being compressed, in
 which case you may want to use the --compressed option.
+
+Starting in curl 8.21.0, the separate globbing parts can be named and
+referenced by their names. The case sensitive alphanumeric name is set
+enclosed within angle brackets after the opening character. Examples:
+
+    curl "https://fun.example/{<num>one,two}.jpg" -o "save-#<num>"
+
+    curl "ftp://ftp.example/file[<range>1-100].txt" \
+      -o "save-#<range>.txt"
+
+Referencing a named glob that is not set, causes an error.