hsts: add support for Strict-Transport-Security

- enable in the build (configure)
- header parsing
- host name lookup
- unit tests for the above
- CI build
- CURL_VERSION_HSTS bit
- curl_version_info support
- curl -V output
- curl-config --features
- CURLOPT_HSTS_CTRL
- man page for CURLOPT_HSTS_CTRL
- curl --hsts (sets CURLOPT_HSTS_CTRL and works with --libcurl)
- man page for --hsts
- save cache to disk
- load cache from disk
- CURLOPT_HSTS
- man page for CURLOPT_HSTS
- added docs/HSTS.md
- fixed --version docs
- adjusted curl_easy_duphandle

Closes #5896

1 files changed, 4 insertions, 0 deletions

diff --git a/src/tool_help.c b/src/tool_help.c
index 544dbbab0..0833a0d23 100644
--- a/src/tool_help.c
+++ b/src/tool_help.c
@@ -328,6 +328,9 @@ static const struct helptxt helptext[] = {
   {"    --hostpubmd5 <md5>",
    "Acceptable MD5 hash of the host public key",
    CURLHELP_SFTP | CURLHELP_SCP},
+  {"    --hsts <file name>",
+   "Enable HSTS with this cache file",
+   CURLHELP_HTTP},
   {"    --http0.9",
    "Allow HTTP 0.9 responses",
    CURLHELP_HTTP},
@@ -862,6 +865,7 @@ static const struct feat feats[] = {
   {"MultiSSL",       CURL_VERSION_MULTI_SSL},
   {"PSL",            CURL_VERSION_PSL},
   {"alt-svc",        CURL_VERSION_ALTSVC},
+  {"HSTS",           CURL_VERSION_HSTS},
 };
 
 static void print_category(curlhelp_t category)