Auto merge of #2763 - micbou:update-clear-compilation-flag-cache-docs, r=vheon

[READY] Update ClearCompilationFlagCache docs

Update the documentation for the `ClearCompilationFlagCache` subcommand by taking into account that:
 - the `do_cache` parameter is set to `True` by default;
 - the flags from the compilation database are also cached;
 - restarting the server clears the cache.

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README.md

@@ -1605,12 +1605,13 @@ Supported in filetypes: `cs, go, javascript, python, rust, typescript`
 #### The `ClearCompilationFlagCache` subcommand
 
 YCM caches the flags it gets from the `FlagsForFile` function in your
-`ycm_extra_conf.py` file if you return them with the `do_cache` parameter set to
-`True`. The cache is in memory and is never invalidated (unless you restart Vim
-of course).
+`ycm_extra_conf.py` file unless you return them with the `do_cache` parameter
+set to `False`. It also caches the flags extracted from the compilation
+database. The cache is in memory and is never invalidated (unless you restart
+the server with the `:YcmRestartServer` command).
 
 This command clears that cache entirely. YCM will then re-query your
-`FlagsForFile` function as needed in the future.
+`FlagsForFile` function or your compilation database as needed in the future.
 
 Supported in filetypes: `c, cpp, objc, objcpp`
 

doc/youcompleteme.txt

@@ -1896,12 +1896,13 @@ Supported in filetypes: 'cs, go, javascript, python, rust, typescript'
 The *ClearCompilationFlagCache* subcommand
 
 YCM caches the flags it gets from the 'FlagsForFile' function in your
-'ycm_extra_conf.py' file if you return them with the 'do_cache' parameter set
-to 'True'. The cache is in memory and is never invalidated (unless you restart
-Vim of course).
+'ycm_extra_conf.py' file unless you return them with the 'do_cache' parameter
+set to 'False'. It also caches the flags extracted from the compilation
+database. The cache is in memory and is never invalidated (unless you restart
+the server with the |:YcmRestartServer| command).
 
 This command clears that cache entirely. YCM will then re-query your
-'FlagsForFile' function as needed in the future.
+'FlagsForFile' function or your compilation database as needed in the future.
 
 Supported in filetypes: 'c, cpp, objc, objcpp'