fs: Add global flag '--color' to control terminal colors

* fs: add TerminalColorMode type
* fs: add new config(flags) for TerminalColorMode
* lib/terminal: use TerminalColorMode to determine how to handle colors
* Add documentation for '--terminal-color-mode'
* tree: remove obsolete --color replaced by global --color

This changes the default behaviour of tree. It now displays colors by
default instead of only displaying them when the flag -C/--color was
active. Old behaviour (no color) can be achieved by setting --color to
'never'.

Fixes: #6604

docs/content/commands/rclone_tree.md

@@ -48,7 +48,6 @@ rclone tree remote:path [flags]
 
 ```
   -a, --all             All files are listed (list . files too)
-  -C, --color           Turn colorization on always
   -d, --dirs-only       List directories only
       --dirsfirst       List directories before files (-U disables)
       --full-path       Print the full path prefix for each file

docs/content/docs.md

@@ -823,6 +823,16 @@ quicker than without the `--checksum` flag.
 When using this flag, rclone won't update mtimes of remote files if
 they are incorrect as it would normally.
 
+### --color WHEN ###
+
+Specifiy when colors (and other ANSI codes) should be added to the output.
+
+`AUTO` (default) only allows ANSI codes when the output is a terminal
+
+`NEVER` never allow ANSI codes
+
+`ALWAYS` always add ANSI codes, regardless of the output format (terminal or file)
+
 ### --compare-dest=DIR ###
 
 When using `sync`, `copy` or `move` DIR is checked in addition to the

docs/content/flags.md

@@ -27,6 +27,7 @@ These flags are available for every command.
   -c, --checksum                             Skip based on checksum (if available) & size, not mod-time & size
       --client-cert string                   Client SSL certificate (PEM) for mutual TLS auth
       --client-key string                    Client SSL private key (PEM) for mutual TLS auth
+      --color                                Define when colors (and other ANSI codes) should be shown AUTO|ALWAYS|NEVER (default AUTO)
       --compare-dest stringArray             Include additional comma separated server-side paths during comparison
       --config string                        Config file (default "$HOME/.config/rclone/rclone.conf")
       --contimeout duration                  Connect timeout (default 1m0s)