curl: add --follow

Makes curl follow redirects an act on the response code and change a
custom method accordingly, contrary to --location.

Potential future command line to send QUERY and following a redirect
according to the status code:

    curl -d "request-body" -X QUERY --follow https://example.com

add test 794,796,797

Assisted-by: Daniel Böhmer <post@daniel-boehmer.de>

Closes #16543

docs/cmdline-opts/Makefile.inc

@@ -101,6 +101,7 @@ DPAGES = \
   fail-with-body.md \
   fail.md \
   false-start.md \
+  follow.md \
   form-escape.md \
   form-string.md \
   form.md \

docs/cmdline-opts/follow.md

@@ -0,0 +1,25 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Long: follow
+Help: Follow redirects per spec
+Category: http
+Added: 8.16.0
+Multi: boolean
+See-also:
+  - request
+  - location
+Example:
+  - -X POST --follow $URL
+---
+
+# `--follow`
+
+Instructs curl to follow HTTP redirects and to do the custom request method
+set with --request when following redirects as the HTTP specification says.
+
+The method string set with --request is used in subsequent requests for the
+status codes 307 or 308, but may be reset to GET for 301, 302 and 303.
+
+This is subtly different than --location, as that option always set the custom
+method in all subsequent requests independent of response code.

docs/cmdline-opts/location-trusted.md

@@ -9,6 +9,7 @@ Added: 7.10.4
 Multi: boolean
 See-also:
   - user
+  - follow
 Example:
   - --location-trusted -u user:password $URL
   - --location-trusted -H "Cookie: session=abc" $URL

docs/cmdline-opts/location.md

@@ -11,6 +11,7 @@ Multi: boolean
 See-also:
   - resolve
   - alt-svc
+  - follow
 Example:
   - -L $URL
 ---

docs/options-in-versions

@@ -199,6 +199,7 @@
 --range (-r)                         4.0
 --rate                               7.84.0
 --raw                                7.16.2
+--follow                             8.16.0
 --referer (-e)                       4.0
 --remote-header-name (-J)            7.20.0
 --remote-name (-O)                   4.0