Summary:
.clangd/index was well-intentioned in 2754942c, but `.clangd` is the best
filename for the clangd config file (matching .clang-format and .clang-tidy).
And of course we can't have both .clangd/index and .clangd...

There are a few overlapping goals to satisfy:
 - it should be clear from the directory name that this is transient
   data that is safe to delete at the cost of recomputation, i.e. a cache
 - it should be easy and self-documenting to blacklist these files in .gitignore
 - we should have some consistency between filenames in-tree and
   corresponding files in user storage (e.g. under XDG's ~/.cache/)
 - we should be consistent across platforms (including windows, which
   doesn't have distinct cache vs config directories)

So the plan is:
  $PROJECT/.clangd                    (project config)
  $PROJECT/.cache/clangd/index/       (project index)
  $PROJECT/.cache/clangd/modules/     (maybe in future)
  $XDG_CONFIG_HOME/clangd/config.yaml (user config)
  $XDG_CACHE_HOME/clangd/index/       (index of non-project files)
  $XDG_CACHE_HOME/clangd/modules/     (maybe in future)
This is sensible if XDG_{CONFIG,CACHE}_HOME coincide, and has a simple
.gitignore rule going forward: `.cache/`.

The monorepo gitignore is updated to reflect the backwards-compatible practice:
  ignore .clangd/ (with trailing slash) matching index files from clangd 9/10
  ignore .cache matching index from clangd 11+, and potentially other tools.
The entries from llvm-project/llvm gitignore are removed (obsolete).

Reviewers: kadircet, hokein

Subscribers: ilya-biryukov, MaskRay, jkorous, omtcyfz, arphaman, usaxena95, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D83099

Differential Revision: https://reviews.llvm.org/D81592

Differential Revision: https://reviews.llvm.org/D81331

llvm-svn: 370841

Reviewers: beanz

Differential Revision: https://reviews.llvm.org/D65559

llvm-svn: 367641

as a start for the monorepo .gitignore.

llvm-svn: 357961

Patch by Guansong Zhang.

Differential Revision: https://reviews.llvm.org/D30784

llvm-svn: 297562

That is where the documentation gets built to.

I'm pretty much clueless about SVN; I would appreciate if someone more
knowledgeable about SVN made the equivalent change.

llvm-svn: 176417

    
Reviewers: klimek

llvm-svn: 172414

This is just the output of sphinx-quickstart. Now all that is needed
to begin converting the analyzer docs to reST is the server-side setup.

The analyzer folks have asked me to keep this segregated from the other
clang docs since the analyzer is a logically separate project (and has
its own separate web page) even though it resides in the clang tree.

llvm-svn: 171425

I don't think this will be visible just yet on <clang.llvm.org/docs/>
since I don't think that the necessary server-side setup has taken
place.

Don't shoot me over the theme. I don't want to duplicate LLVM's theme
into the clang repo at the moment, so I just used one of Sphinx's
default themes.

llvm-svn: 170042

llvm-svn: 165570

llvm-svn: 161764

llvm-svn: 142792

llvm-svn: 142791

llvm-svn: 135440

llvm-svn: 132365

llvm-svn: 122066

llvm-svn: 121985

llvm-svn: 121968

of the entries there are useless for out of source builds.

llvm-svn: 121955