[clangd] Add documentation page

[malaperle-ericsson]

Summary

Add a simple documentation page for Clangd.
This will be useful for interested users and contributors to get basic information about how
to get started and the progress of Clangd.

[xazax.hun]

Maybe this is a good time to decide ClangD, Clangd, or clangd is the correct capitalization.

[kromanenkov]

docs/clangd.rst

11

s/Languge/Language

17

s/developpers/developers

35

s/satus/status

94

s/Languge/Language

[JonasToth]

docs/clangd.rst

17

maybe there should be special highlighting to Clangd here and elsewhere?

24

maybe remove the you can. The sentence is still valid without the repetition.

[malaperle-ericsson]

Fixed typos and other comments.

[malaperle-ericsson]

Sorry about all the typos. I have now installed a spell checked in VS Code :)

[mgehre]

docs/clangd.rst

28

In the reference, it is called "extra Clang tools".

[malaperle-ericsson]

Fix mention of "extra Clang tools"

[JDevlieghere]

Great to see this coming along!

docs/clangd.rst

11

s/clangd/Clangd

11

Reflow text to 80 columns

21

Spurious backticks

23

Spurious backtick

34

Spurious backtick

36

Spurious backtick

38

Spurious backtick

92

:program:Clangd

95

:program:Clangd

[malaperle-ericsson]

Update with comments (extra backticks, etc)

[malaperle-ericsson]

Ping. Any more objections?

[JDevlieghere]

Looks good, nothing to add from my side.

[malaperle-ericsson]

Would it be possible to commit this? I do not have commit rights. Thanks!

[Prazek]

In D31887#740727, @malaperle-ericsson wrote:

Would it be possible to commit this? I do not have commit rights. Thanks!

Why won't you get commit right? You will probably make some other contribution to clangd, so it will be handy to have it :)

[malaperle-ericsson]

In D31887#740747, @Prazek wrote:

In D31887#740727, @malaperle-ericsson wrote:

Would it be possible to commit this? I do not have commit rights. Thanks!

Why won't you get commit right? You will probably make some other contribution to clangd, so it will be handy to have it :)

I wasn't sure at what moment it was appropriate to ask for commit rights. I just sent the request for it :)

[krasimir]

Looks good! Thank you!

docs/clangd.rst

+============
+Clangd
+============
+
+.. contents::
+
+.. toctree::
+   :maxdepth: 1
+
+:program:`clangd` is an implementation of the `Language Server Protocol <https://github.com/Microsoft/language-server-protocol>`_ leveraging Clang.
+Clangd's goal is to provide language "smartness" features like code completion, find references, etc. for clients such as C/C++ Editors.
+
+Using Clangd
+==================
+
+:program:`Clangd` is not meant to be used by C/C++ developers directly but rather from a client implementing the protocol.
+A client would be typically implemented in an IDE or an editor.
+
+At the moment, `Visual Studio Code <https://code.visualstudio.com/>`_ is mainly used
+in order to test :program:`Clangd`` but more clients are likely to make use of :program:`Clangd`` in the
+future as it matures and becomes a production quality tool. If you are interested
+in trying :program:`Clangd`` in combination with Visual Studio Code, you can start by `building Clangd`_,
+then open Visual Studio Code in the clangd-vscode folder and launch the extension.
+
+Building Clangd
+==================
+
+You can follow the instructions for `building Clang <https://clang.llvm.org/get_started.html>`_ but "extra Clang Tool" is **not** optional.
+
+Current Status
+==================
+
+Many features could be implemented in :program:`Clangd``.
+Here is a list of features that could be useful with the status of whether or
+not they are already implemented in :program:`Clangd`` and specified in the Language Server Protocol.
+Note that for some of the features, it is not clear whether or not they should be part of the
+Language Server Protocol, so those features might be eventually developed outside :program:`Clangd``.
+
++-------------------------------------+------------+----------+
+| C/C++ Editor feature                |  LSP       |  Clangd  |
++=====================================+============+==========+
+| Formatting                          | Yes        |   Yes    |
++-------------------------------------+------------+----------+
+| Completion                          | Yes        |   Yes    |
++-------------------------------------+------------+----------+
+| Diagnostics                         | Yes        |   Yes    |
++-------------------------------------+------------+----------+ 
+| Fix-its                             | Yes        |   Yes    |
++-------------------------------------+------------+----------+
+| Go to Definition                    | Yes        |   No     |
++-------------------------------------+------------+----------+
+| Source hover                        | Yes        |   No     |
++-------------------------------------+------------+----------+
+| Signature Help                      | Yes        |   No     |
++-------------------------------------+------------+----------+
+| Find References                     | Yes        |   No     |
++-------------------------------------+------------+----------+
+| Document Highlights                 | Yes        |   No     |
++-------------------------------------+------------+----------+
+| Rename                              | Yes        |   No     |
++-------------------------------------+------------+----------+
+| Code Lens                           | Yes        |   No     |
++-------------------------------------+------------+----------+
+| Syntax and Semantic Coloring        | No         |   No     |
++-------------------------------------+------------+----------+
+| Code folding                        | No         |   No     |
++-------------------------------------+------------+----------+
+| Call hierarchy                      | No         |   No     |
++-------------------------------------+------------+----------+
+| Type hierarchy                      | No         |   No     |
++-------------------------------------+------------+----------+
+| Organize Includes                   | No         |   No     |
++-------------------------------------+------------+----------+
+| Quick Assist                        | No         |   No     |
++-------------------------------------+------------+----------+
+| Extract Local Variable              | No         |   No     |
++-------------------------------------+------------+----------+
+| Extract Function/Method             | No         |   No     |
++-------------------------------------+------------+----------+
+| Hide Method                         | No         |   No     |
++-------------------------------------+------------+----------+
+| Implement Method                    | No         |   No     |
++-------------------------------------+------------+----------+
+| Gen. Getters/Setters                | No         |   No     |
++-------------------------------------+------------+----------+
+
+Getting Involved
+==================
+
+A good place for interested contributors is the `Clang developer mailing list <http://lists.llvm.org/mailman/listinfo/cfe-dev>`_.
+If you're also interested in contributing patches to Clangd, take a look at the
+`LLVM Developer Policy <http://llvm.org/docs/DeveloperPolicy.html>`_ and `Code Reviews <http://llvm.org/docs/Phabricator.html>`_ page.
+Contributions of new features to the `Language Server Protocol <https://github.com/Microsoft/language-server-protocol>`_ itself would also be very useful,
+so that Clangd can eventually implement them in a conforming way.
 No newline at end of file

docs/index.rst

 .. toctree::
    :maxdepth: 2
 
    clang-tidy/index
    include-fixer
    modularize
    pp-trace
    clang-rename
+   clangd
 
 
 Doxygen Documentation
 =====================
 The Doxygen documentation describes the **internal** software that makes up the
 tools of clang-tools-extra, not the **external** use of these tools. The Doxygen
 documentation contains no instructions about how to use the tools, only the APIs
 that make up the software. For usage instructions, please see the user's guide