[clang-format] Filter options dumped by `-dump-config`

[SunBlack]

When we switch to a new version of Clang format, I currently always use -dump-config > .clang-format_new in the folder where our currently used config file is located and then do a diff on the files to see what has changed since the last update, so I don't have to go through the changelogs of different versions (and the missing entries in them like the new TableGen options in the changelog of CF 19).

Clang-Format currently dumps all options, even if they are not relevant. For example, there are Java entries in the C++ block, which is currently not so easy to recognize (see also #134390).

So the dumped file looks, e.g., like:

---
Language:        Cpp
# ...
AllowShortCaseExpressionOnASingleLine: true
# ...
...

As the yml files supports multiple languages within a single config file, I would expect sth. like this:

---
Language:        Cpp
# ...
---
Language:        Java
AllowShortCaseExpressionOnASingleLine: true
# ...
...

So I suggest improving -dump-config by following things:

1. In case LanguageKind is None it could still print all options within this block
2. If a specific language (or multiple) is configured, only output options for this language (filtering) within the block.
3. In case there is a None-Language-Block and a (or multiple) specific blocks: In case an option is just for a specific language, add the option just in this block, otherwise in the general block.

[llvmbot]

@llvm/issue-subscribers-clang-format

Author: SunBlack (SunBlack)

When we switch to a new version of Clang format, I currently always use `-dump-config > .clang-format_new` in the folder where our currently used config file is located and then do a diff on the files to see what has changed since the last update, so I don't have to go through the changelogs of different versions (and the missing entries in them like the new TableGen options in the changelog of CF 19).

Clang-Format currently dumps all options, even if they are not relevant. For example, there are Java entries in the C++ block, which is currently not so easy to recognize (see also #134390).

So the dumped file looks, e.g., like:

---
Language:        Cpp
# ...
AllowShortCaseExpressionOnASingleLine: true
# ...
...

As the yml files supports multiple languages within a single config file, I would expect sth. like this:

---
Language:        Cpp
# ...
---
Language:        Java
AllowShortCaseExpressionOnASingleLine: true
# ...
...

So I suggest improving -dump-config by following things:

1. In case LanguageKind is None it could still print all options within this block
2. If a specific language (or multiple) is configured, only output options for this language (filtering) within the block.
3. In case there is a None-Language-Block and a (or multiple) specific blocks: In case an option is just for a specific language, add the option just in this block, otherwise in the general block.