Failures clearly returned from a (SOCKS) proxy now causes this return
code. Previously the situation was not very clear as what would be
returned and when.

In addition: when this error code is returned, an application can use
CURLINFO_PROXY_ERROR to query libcurl for the detailed error, which then
returns a value from the new 'CURLproxycode' enum.

Fixes the line endings on Windows.

Closes https://github.com/curl/curl/pull/5767

These are only called for WIN32.

Closes https://github.com/curl/curl/pull/5767

... and rephrase that "not all" TLS backends support it.

Closes #5764

Ref: #5763
Closes #5764

Closes https://github.com/curl/curl/pull/5754

Closes https://github.com/curl/curl/pull/5754

This makes the tests that require the OpenSSL feature also run for
those two compatible libraries.

Closes https://github.com/curl/curl/pull/5762

Reported by Codacy.

Reviewed-by: Marcel Raad
Closes #5759

`SSL_CTX_add0_chain_cert` and `SSL_CTX_clear_chain_certs` were
introduced in LibreSSL 2.9.1 [0].

[0] https://github.com/libressl-portable/openbsd/commit/0db809ee178457c8170abfae3931d7bd13abf3ef

Closes https://github.com/curl/curl/pull/5757

Previously any connect-only connections in a multi handle would be kept
alive until the multi handle was closed.  Since these connections cannot
be re-used, they can be marked for closure when the associated easy
handle is removed from the multi handle.

Closes #5749

Without the -D command line option, checksrc.pl won't know which
directory to load the ".checksrc" file from when building out of the
source tree.

Reported-by: Marcel Raad
Fixes #5715
Closes #5755

no longer needed after 4259d2df

retired with 09f27812 but kept around as
the name is generic enough that it might be in use and relied upon from
the environment.

reported as error SC2145[1] by shellcheck, but not expected to cause
any behavioural differences otherwise.

[1] https://github.com/koalaman/shellcheck/wiki/SC2145

Closes #5701

Closes #5752

Reviewed-by: Daniel Stenberg

Closes #5708

Follow up to #5721

This enables building and running the SFTP tests.
Unfortunately OpenSSH for Windows does not support SCP (yet).

Reviewed-by: Daniel Stenberg

Closes #5721

Avoid aborted jobs due to performance issues on Azure DevOps.

Reviewed-by: Daniel Stenberg
Reviewed-by: Jay Satiro

Closes #5738

We should offer an option to allow abrupt server closures (server closes
SSL transfer without sending a known termination point such as length of
transfer or close_notify alert). Abrupt server closures are usually
because of misconfigured or very old servers.

Closes https://github.com/curl/curl/issues/4427

Prior to this change if the user set a URL handle (CURLOPT_CURLU) it was
incorrectly used for the location follow, resulting in infinite requests
to the original location.

Reported-by:  <sspiri@users.noreply.github.com>

Fixes https://github.com/curl/curl/issues/5709
Closes https://github.com/curl/curl/pull/5713

it helps make it obvious that most developers don't have to care about
the CURLM_CALL_MULTI_PERFORM value (last release using it is nearly 11
years old, November 4 2009)

Closes #5744

- Use S_IREAD and S_IWRITE mode permission flags to create the file
  on Windows instead of S_IRUSR, S_IWUSR, etc.

Windows only accepts a combination of S_IREAD and S_IWRITE. It does not
acknowledge other combinations, for which it may generate an assertion.

This is a follow-up to 81b4e99b from yesterday, which improved the
existing file check with -J.

Ref: https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/open-wopen#remarks
Ref: https://github.com/curl/curl/pull/5731

Closes https://github.com/curl/curl/pull/5742

They're not thread-safe so they should not be used in libcurl code.

Explictly enabled when deemed necessary and in examples and tests

Reviewed-by: Nicolas Sterchele
Closes #5732

Closes #5734

On systems with 32 bit long the expression is always false. Avoid
the warning.

Reported-by: Gisle Vanem
Bug: https://github.com/curl/curl/commit/61a08508f6a458fe21bbb18cd2a9bac2f039452b#commitcomment-40941232
Closes #5736

Previously a file that isn't user-readable but is user-writable would
not be properly avoided and would get overwritten.

Reported-by: BrumBrum on hackerone
Assisted-by: Jay Satiro
Bug: https://hackerone.com/reports/926638
Closes #5731

Since 09b9fc90

 (multi: remove 'Curl_one_easy' struct, phase 1,
2013-08-02), the easy handle list is not circular but ends with
->next pointing to NULL.

Reported-by: Masaya Suzuki <masayasuzuki@google.com>
Closes #5737

As test 1140 fails otherwise!

Follow-up to e1bac81c

Reported-by: Tatsuhiro Tsujikawa
Closes #5733

... and mention that HTTP with other methods than HEAD might get a body and
there's no option available to stop that.

Closes #5729

Unsetting CURLOPT_NOBODY with 0L when doing HTTP has no documented
action but before 7.71.0 that used to switch back to GET and with this
change (assuming the method is still set to HEAD) this behavior is
brought back.

Reported-by: causal-agent on github
Fixes #5725
Closes #5728