Expose the nix component in header include paths

For example, instead of doing

    #include "nix/store-config.hh"
    #include "nix/derived-path.hh"

Now do

    #include "nix/store/config.hh"
    #include "nix/store/derived-path.hh"

This was originally planned in the issue, and also recent requested by
Eelco.

Most of the change is purely mechanical. There is just one small
additional issue. See how, in the example above, we took this
opportunity to also turn `<comp>-config.hh` into `<comp>/config.hh`.
Well, there was already a `nix/util/config.{cc,hh}`. Even though there
is not a public configuration header for libutil (which also would be
called `nix/util/config.{cc,hh}`) that's still confusing, To avoid any
such confusion, we renamed that to `nix/util/configuration.{cc,hh}`.

Finally, note that the libflake headers already did this, so we didn't
need to do anything to them. We wouldn't want to mistakenly get
`nix/flake/flake/flake.hh`!

Progress on #7876

Author: Ericson2314

doc/manual/source/development/testing.md

@@ -30,8 +30,8 @@ The unit tests are defined using the [googletest] and [rapidcheck] frameworks.
 > src
 > ├── libexpr
 > │   ├── meson.build
-> │   ├── value/context.hh
-> │   ├── include/nix/value/context.cc
+> │   ├── include/nix/expr/value/context.hh
+> │   ├── value/context.cc
 > │   …
 > │
 > ├── tests
@@ -46,7 +46,7 @@ The unit tests are defined using the [googletest] and [rapidcheck] frameworks.
 > │   │
 > │   ├── libexpr-test-support
 > │   │   ├── meson.build
-> │   │   ├── include/nix
+> │   │   ├── include/nix/expr
 > │   │   │   ├── meson.build
 > │   │   │   └── tests
 > │   │   │       ├── value/context.hh
@@ -63,7 +63,7 @@ The unit tests are defined using the [googletest] and [rapidcheck] frameworks.
 > ```
 
 The tests for each Nix library (`libnixexpr`, `libnixstore`, etc..) live inside a directory `src/${library_name_without-nix}-test`.
-Given an interface (header) and implementation pair in the original library, say, `src/libexpr/include/nix/value/context.hh` and `src/libexpr/value/context.cc`, we write tests for it in `src/libexpr-tests/value/context.cc`, and (possibly) declare/define additional interfaces for testing purposes in `src/libexpr-test-support/include/nix/tests/value/context.hh` and `src/libexpr-test-support/tests/value/context.cc`.
+Given an interface (header) and implementation pair in the original library, say, `src/libexpr/include/nix/expr/value/context.hh` and `src/libexpr/value/context.cc`, we write tests for it in `src/libexpr-tests/value/context.cc`, and (possibly) declare/define additional interfaces for testing purposes in `src/libexpr-test-support/include/nix/expr/tests/value/context.hh` and `src/libexpr-test-support/tests/value/context.cc`.
 
 Data for unit tests is stored in a `data` subdir of the directory for each unit test executable.
 For example, `libnixstore` code is in `src/libstore`, and its test data is in `src/libstore-tests/data`.

maintainers/flake-module.nix

@@ -9,19 +9,19 @@
 #include <sys/time.h>
 #endif
 
-#include "nix/machines.hh"
-#include "nix/shared.hh"
-#include "nix/plugin.hh"
-#include "nix/pathlocks.hh"
-#include "nix/globals.hh"
-#include "nix/serialise.hh"
-#include "nix/build-result.hh"
-#include "nix/store-api.hh"
-#include "nix/strings.hh"
-#include "nix/derivations.hh"
-#include "nix/local-store.hh"
-#include "nix/legacy.hh"
-#include "nix/experimental-features.hh"
+#include "nix/store/machines.hh"
+#include "nix/main/shared.hh"
+#include "nix/main/plugin.hh"
+#include "nix/store/pathlocks.hh"
+#include "nix/store/globals.hh"
+#include "nix/util/serialise.hh"
+#include "nix/store/build-result.hh"
+#include "nix/store/store-api.hh"
+#include "nix/util/strings.hh"
+#include "nix/store/derivations.hh"
+#include "nix/store/local-store.hh"
+#include "nix/cmd/legacy.hh"
+#include "nix/util/experimental-features.hh"
 
 using namespace nix;
 using std::cin;

src/build-remote/build-remote.cc

@@ -1,7 +1,7 @@
-#include "nix/built-path.hh"
-#include "nix/derivations.hh"
-#include "nix/store-api.hh"
-#include "nix/comparator.hh"
+#include "nix/cmd/built-path.hh"
+#include "nix/store/derivations.hh"
+#include "nix/store/store-api.hh"
+#include "nix/util/comparator.hh"
 
 #include <nlohmann/json.hpp>
 

src/libcmd/built-path.cc

@@ -1,4 +1,4 @@
-#include "nix/command-installable-value.hh"
+#include "nix/cmd/command-installable-value.hh"
 
 namespace nix {
 

src/libcmd/command-installable-value.cc

@@ -1,16 +1,16 @@
 #include <algorithm>
 #include <nlohmann/json.hpp>
 
-#include "nix/command.hh"
-#include "nix/markdown.hh"
-#include "nix/store-api.hh"
-#include "nix/local-fs-store.hh"
-#include "nix/derivations.hh"
-#include "nix/nixexpr.hh"
-#include "nix/profiles.hh"
-#include "nix/repl.hh"
-#include "nix/strings.hh"
-#include "nix/environment-variables.hh"
+#include "nix/cmd/command.hh"
+#include "nix/cmd/markdown.hh"
+#include "nix/store/store-api.hh"
+#include "nix/store/local-fs-store.hh"
+#include "nix/store/derivations.hh"
+#include "nix/expr/nixexpr.hh"
+#include "nix/store/profiles.hh"
+#include "nix/cmd/repl.hh"
+#include "nix/util/strings.hh"
+#include "nix/util/environment-variables.hh"
 
 namespace nix {
 

src/libcmd/command.cc

@@ -1,20 +1,20 @@
-#include "nix/fetch-settings.hh"
-#include "nix/eval-settings.hh"
-#include "nix/common-eval-args.hh"
-#include "nix/shared.hh"
-#include "nix/config-global.hh"
-#include "nix/filetransfer.hh"
-#include "nix/eval.hh"
-#include "nix/fetchers.hh"
-#include "nix/registry.hh"
+#include "nix/fetchers/fetch-settings.hh"
+#include "nix/expr/eval-settings.hh"
+#include "nix/cmd/common-eval-args.hh"
+#include "nix/main/shared.hh"
+#include "nix/util/config-global.hh"
+#include "nix/store/filetransfer.hh"
+#include "nix/expr/eval.hh"
+#include "nix/fetchers/fetchers.hh"
+#include "nix/fetchers/registry.hh"
 #include "nix/flake/flakeref.hh"
 #include "nix/flake/settings.hh"
-#include "nix/store-api.hh"
-#include "nix/command.hh"
-#include "nix/tarball.hh"
-#include "nix/fetch-to-store.hh"
-#include "nix/compatibility-settings.hh"
-#include "nix/eval-settings.hh"
+#include "nix/store/store-api.hh"
+#include "nix/cmd/command.hh"
+#include "nix/fetchers/tarball.hh"
+#include "nix/fetchers/fetch-to-store.hh"
+#include "nix/cmd/compatibility-settings.hh"
+#include "nix/expr/eval-settings.hh"
 
 namespace nix {
 

src/libcmd/common-eval-args.cc

@@ -1,6 +1,6 @@
-#include "nix/editor-for.hh"
-#include "nix/environment-variables.hh"
-#include "nix/source-path.hh"
+#include "nix/cmd/editor-for.hh"
+#include "nix/util/environment-variables.hh"
+#include "nix/util/source-path.hh"
 
 namespace nix {
 

src/libcmd/editor-for.cc

@@ -1,8 +1,8 @@
 #pragma once
 ///@file
 
-#include "nix/derived-path.hh"
-#include "nix/realisation.hh"
+#include "nix/store/derived-path.hh"
+#include "nix/store/realisation.hh"
 
 namespace nix {
 

src/libcmd/include/nix/built-path.hh renamed to src/libcmd/include/nix/cmd/built-path.hh

@@ -1,8 +1,8 @@
 #pragma once
 ///@file
 
-#include "nix/installable-value.hh"
-#include "nix/command.hh"
+#include "nix/cmd/installable-value.hh"
+#include "nix/cmd/command.hh"
 
 namespace nix {