Separate headers from source files

The short answer for why we need to do this is so we can consistently do
`#include "nix/..."`. Without this change, there are ways to still make
that work, but they are hacky, and they have downsides such as making it
harder to make sure headers from the wrong Nix library (e..g.
`libnixexpr` headers in `libnixutil`) aren't being used.

The C API alraedy used `nix_api_*`, so its headers are *not* put in
subdirectories accordingly.

Progress on #7876

We resisted doing this for a while because it would be annoying to not
have the header source file pairs close by / easy to change file
path/name from one to the other. But I am ameliorating that with
symlinks in the next commit.

src/libcmd/built-path.cc

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

src/libcmd/command-installable-value.cc

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

src/libcmd/command.cc

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

src/libcmd/common-eval-args.cc

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

src/libcmd/editor-for.cc

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

src/libcmd/include/nix/built-path.hh

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

src/libcmd/include/nix/command-installable-value.hh

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

src/libcmd/include/nix/command.hh

@@ -1,11 +1,11 @@
 #pragma once
 ///@file
 
-#include "installable-value.hh"
-#include "args.hh"
-#include "common-eval-args.hh"
-#include "path.hh"
-#include "flake/lockfile.hh"
+#include "nix/installable-value.hh"
+#include "nix/args.hh"
+#include "nix/common-eval-args.hh"
+#include "nix/path.hh"
+#include "nix/flake/lockfile.hh"
 
 #include <optional>
 

src/libcmd/include/nix/common-eval-args.hh

@@ -1,10 +1,10 @@
 #pragma once
 ///@file
 
-#include "args.hh"
-#include "canon-path.hh"
-#include "common-args.hh"
-#include "search-path.hh"
+#include "nix/args.hh"
+#include "nix/canon-path.hh"
+#include "nix/common-args.hh"
+#include "nix/search-path.hh"
 
 #include <filesystem>
 

src/libcmd/include/nix/compatibility-settings.hh

@@ -1,5 +1,5 @@
 #pragma once
-#include "config.hh"
+#include "nix/config.hh"
 
 namespace nix {
 struct CompatibilitySettings : public Config

src/libcmd/include/nix/editor-for.hh

@@ -1,8 +1,8 @@
 #pragma once
 ///@file
 
-#include "types.hh"
-#include "source-path.hh"
+#include "nix/types.hh"
+#include "nix/source-path.hh"
 
 namespace nix {
 

src/libcmd/include/nix/installable-attr-path.hh

@@ -1,22 +1,22 @@
 #pragma once
 ///@file
 
-#include "globals.hh"
-#include "installable-value.hh"
-#include "outputs-spec.hh"
-#include "command.hh"
-#include "attr-path.hh"
-#include "common-eval-args.hh"
-#include "derivations.hh"
-#include "eval-inline.hh"
-#include "eval.hh"
-#include "get-drvs.hh"
-#include "store-api.hh"
-#include "shared.hh"
-#include "eval-cache.hh"
-#include "url.hh"
-#include "registry.hh"
-#include "build-result.hh"
+#include "nix/globals.hh"
+#include "nix/installable-value.hh"
+#include "nix/outputs-spec.hh"
+#include "nix/command.hh"
+#include "nix/attr-path.hh"
+#include "nix/common-eval-args.hh"
+#include "nix/derivations.hh"
+#include "nix/eval-inline.hh"
+#include "nix/eval.hh"
+#include "nix/get-drvs.hh"
+#include "nix/store-api.hh"
+#include "nix/shared.hh"
+#include "nix/eval-cache.hh"
+#include "nix/url.hh"
+#include "nix/registry.hh"
+#include "nix/build-result.hh"
 
 #include <regex>
 #include <queue>

src/libcmd/include/nix/installable-derived-path.hh

@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 
-#include "installables.hh"
+#include "nix/installables.hh"
 
 namespace nix {
 

src/libcmd/include/nix/installable-flake.hh

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

src/libcmd/include/nix/installable-value.hh

@@ -1,8 +1,8 @@
 #pragma once
 ///@file
 
-#include "installables.hh"
-#include "flake/flake.hh"
+#include "nix/installables.hh"
+#include "nix/flake/flake.hh"
 
 namespace nix {
 

src/libcmd/include/nix/installables.hh

@@ -1,12 +1,12 @@
 #pragma once
 ///@file
 
-#include "path.hh"
-#include "outputs-spec.hh"
-#include "derived-path.hh"
-#include "built-path.hh"
-#include "store-api.hh"
-#include "build-result.hh"
+#include "nix/path.hh"
+#include "nix/outputs-spec.hh"
+#include "nix/derived-path.hh"
+#include "nix/built-path.hh"
+#include "nix/store-api.hh"
+#include "nix/build-result.hh"
 
 #include <optional>
 

src/libcmd/include/nix/meson.build

@@ -0,0 +1,23 @@
+# Public headers directory
+
+include_dirs = [include_directories('..')]
+
+headers = files(
+  'built-path.hh',
+  'command-installable-value.hh',
+  'command.hh',
+  'common-eval-args.hh',
+  'compatibility-settings.hh',
+  'editor-for.hh',
+  'installable-attr-path.hh',
+  'installable-derived-path.hh',
+  'installable-flake.hh',
+  'installable-value.hh',
+  'installables.hh',
+  'legacy.hh',
+  'markdown.hh',
+  'misc-store-flags.hh',
+  'network-proxy.hh',
+  'repl-interacter.hh',
+  'repl.hh',
+)

src/libcmd/include/nix/misc-store-flags.hh

@@ -1,5 +1,5 @@
-#include "args.hh"
-#include "content-address.hh"
+#include "nix/args.hh"
+#include "nix/content-address.hh"
 
 namespace nix::flag {
 

src/libcmd/include/nix/network-proxy.hh

@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 
-#include "types.hh"
+#include "nix/types.hh"
 
 namespace nix {
 

src/libcmd/include/nix/repl-interacter.hh

@@ -1,8 +1,8 @@
 #pragma once
 /// @file
 
-#include "finally.hh"
-#include "types.hh"
+#include "nix/finally.hh"
+#include "nix/types.hh"
 #include <functional>
 #include <string>
 

src/libcmd/include/nix/repl.hh

@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 
-#include "eval.hh"
+#include "nix/eval.hh"
 
 namespace nix {
 

src/libcmd/installable-attr-path.cc

@@ -1,21 +1,21 @@
-#include "globals.hh"
-#include "installable-attr-path.hh"
-#include "outputs-spec.hh"
-#include "util.hh"
-#include "command.hh"
-#include "attr-path.hh"
-#include "common-eval-args.hh"
-#include "derivations.hh"
-#include "eval-inline.hh"
-#include "eval.hh"
-#include "get-drvs.hh"
-#include "store-api.hh"
-#include "shared.hh"
-#include "flake/flake.hh"
-#include "eval-cache.hh"
-#include "url.hh"
-#include "registry.hh"
-#include "build-result.hh"
+#include "nix/globals.hh"
+#include "nix/installable-attr-path.hh"
+#include "nix/outputs-spec.hh"
+#include "nix/util.hh"
+#include "nix/command.hh"
+#include "nix/attr-path.hh"
+#include "nix/common-eval-args.hh"
+#include "nix/derivations.hh"
+#include "nix/eval-inline.hh"
+#include "nix/eval.hh"
+#include "nix/get-drvs.hh"
+#include "nix/store-api.hh"
+#include "nix/shared.hh"
+#include "nix/flake/flake.hh"
+#include "nix/eval-cache.hh"
+#include "nix/url.hh"
+#include "nix/registry.hh"
+#include "nix/build-result.hh"
 
 #include <regex>
 #include <queue>

src/libcmd/installable-derived-path.cc

@@ -1,5 +1,5 @@
-#include "installable-derived-path.hh"
-#include "derivations.hh"
+#include "nix/installable-derived-path.hh"
+#include "nix/derivations.hh"
 
 namespace nix {
 

src/libcmd/installable-flake.cc

@@ -1,22 +1,22 @@
-#include "globals.hh"
-#include "installable-flake.hh"
-#include "installable-derived-path.hh"
-#include "outputs-spec.hh"
-#include "util.hh"
-#include "command.hh"
-#include "attr-path.hh"
-#include "common-eval-args.hh"
-#include "derivations.hh"
-#include "eval-inline.hh"
-#include "eval.hh"
-#include "get-drvs.hh"
-#include "store-api.hh"
-#include "shared.hh"
-#include "flake/flake.hh"
-#include "eval-cache.hh"
-#include "url.hh"
-#include "registry.hh"
-#include "build-result.hh"
+#include "nix/globals.hh"
+#include "nix/installable-flake.hh"
+#include "nix/installable-derived-path.hh"
+#include "nix/outputs-spec.hh"
+#include "nix/util.hh"
+#include "nix/command.hh"
+#include "nix/attr-path.hh"
+#include "nix/common-eval-args.hh"
+#include "nix/derivations.hh"
+#include "nix/eval-inline.hh"
+#include "nix/eval.hh"
+#include "nix/get-drvs.hh"
+#include "nix/store-api.hh"
+#include "nix/shared.hh"
+#include "nix/flake/flake.hh"
+#include "nix/eval-cache.hh"
+#include "nix/url.hh"
+#include "nix/registry.hh"
+#include "nix/build-result.hh"
 
 #include <regex>
 #include <queue>

src/libcmd/installable-value.cc

@@ -1,6 +1,6 @@
-#include "installable-value.hh"
-#include "eval-cache.hh"
-#include "fetch-to-store.hh"
+#include "nix/installable-value.hh"
+#include "nix/eval-cache.hh"
+#include "nix/fetch-to-store.hh"
 
 namespace nix {
 

src/libcmd/installables.cc

@@ -1,33 +1,33 @@
-#include "globals.hh"
-#include "installables.hh"
-#include "installable-derived-path.hh"
-#include "installable-attr-path.hh"
-#include "installable-flake.hh"
-#include "outputs-spec.hh"
-#include "users.hh"
-#include "util.hh"
-#include "command.hh"
-#include "attr-path.hh"
-#include "common-eval-args.hh"
-#include "derivations.hh"
-#include "eval-inline.hh"
-#include "eval.hh"
-#include "eval-settings.hh"
-#include "get-drvs.hh"
-#include "store-api.hh"
-#include "shared.hh"
-#include "flake/flake.hh"
-#include "eval-cache.hh"
-#include "url.hh"
-#include "registry.hh"
-#include "build-result.hh"
+#include "nix/globals.hh"
+#include "nix/installables.hh"
+#include "nix/installable-derived-path.hh"
+#include "nix/installable-attr-path.hh"
+#include "nix/installable-flake.hh"
+#include "nix/outputs-spec.hh"
+#include "nix/users.hh"
+#include "nix/util.hh"
+#include "nix/command.hh"
+#include "nix/attr-path.hh"
+#include "nix/common-eval-args.hh"
+#include "nix/derivations.hh"
+#include "nix/eval-inline.hh"
+#include "nix/eval.hh"
+#include "nix/eval-settings.hh"
+#include "nix/get-drvs.hh"
+#include "nix/store-api.hh"
+#include "nix/shared.hh"
+#include "nix/flake/flake.hh"
+#include "nix/eval-cache.hh"
+#include "nix/url.hh"
+#include "nix/registry.hh"
+#include "nix/build-result.hh"
 
 #include <regex>
 #include <queue>
 
 #include <nlohmann/json.hpp>
 
-#include "strings-inline.hh"
+#include "nix/strings-inline.hh"
 
 namespace nix {
 

src/libcmd/legacy.cc

@@ -1,4 +1,4 @@
-#include "legacy.hh"
+#include "nix/legacy.hh"
 
 namespace nix {
 

src/libcmd/markdown.cc

@@ -1,8 +1,8 @@
-#include "markdown.hh"
-#include "environment-variables.hh"
-#include "error.hh"
-#include "finally.hh"
-#include "terminal.hh"
+#include "nix/markdown.hh"
+#include "nix/environment-variables.hh"
+#include "nix/error.hh"
+#include "nix/finally.hh"
+#include "nix/terminal.hh"
 
 #include "cmd-config-private.hh"
 

src/libcmd/meson.build

@@ -61,9 +61,9 @@ config_h = configure_file(
 add_project_arguments(
   # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
   # It would be nice for our headers to be idempotent instead.
-  '-include', 'config-util.hh',
-  '-include', 'config-store.hh',
-  '-include', 'config-expr.hh',
+  '-include', 'nix/config-util.hh',
+  '-include', 'nix/config-store.hh',
+  '-include', 'nix/config-expr.hh',
   language : 'cpp',
 )
 
@@ -88,27 +88,7 @@ sources = files(
   'repl.cc',
 )
 
-include_dirs = [include_directories('.')]
-
-headers = files(
-  'built-path.hh',
-  'command-installable-value.hh',
-  'command.hh',
-  'common-eval-args.hh',
-  'compatibility-settings.hh',
-  'editor-for.hh',
-  'installable-attr-path.hh',
-  'installable-derived-path.hh',
-  'installable-flake.hh',
-  'installable-value.hh',
-  'installables.hh',
-  'legacy.hh',
-  'markdown.hh',
-  'misc-store-flags.hh',
-  'network-proxy.hh',
-  'repl-interacter.hh',
-  'repl.hh',
-)
+subdir('include/nix')
 
 subdir('nix-meson-build-support/export-all-symbols')
 subdir('nix-meson-build-support/windows-version')

src/libcmd/misc-store-flags.cc

@@ -1,4 +1,4 @@
-#include "misc-store-flags.hh"
+#include "nix/misc-store-flags.hh"
 
 namespace nix::flag
 {

src/libcmd/network-proxy.cc

@@ -1,8 +1,8 @@
-#include "network-proxy.hh"
+#include "nix/network-proxy.hh"
 
 #include <algorithm>
 
-#include "environment-variables.hh"
+#include "nix/environment-variables.hh"
 
 namespace nix {
 

src/libcmd/package.nix

@@ -46,6 +46,7 @@ mkMesonLibrary (finalAttrs: {
     ./.version
     ./meson.build
     ./meson.options
+    ./include/nix/meson.build
     (fileset.fileFilter (file: file.hasExt "cc") ./.)
     (fileset.fileFilter (file: file.hasExt "hh") ./.)
   ];

src/libcmd/repl-interacter.cc

@@ -16,12 +16,12 @@ extern "C" {
 }
 #endif
 
-#include "signals.hh"
-#include "finally.hh"
-#include "repl-interacter.hh"
-#include "file-system.hh"
-#include "repl.hh"
-#include "environment-variables.hh"
+#include "nix/signals.hh"
+#include "nix/finally.hh"
+#include "nix/repl-interacter.hh"
+#include "nix/file-system.hh"
+#include "nix/repl.hh"
+#include "nix/environment-variables.hh"
 
 namespace nix {
 

src/libcmd/repl.cc

@@ -2,34 +2,34 @@
 #include <cstdlib>
 #include <cstring>
 
-#include "error.hh"
-#include "repl-interacter.hh"
-#include "repl.hh"
+#include "nix/error.hh"
+#include "nix/repl-interacter.hh"
+#include "nix/repl.hh"
 
-#include "ansicolor.hh"
-#include "shared.hh"
-#include "eval.hh"
-#include "eval-settings.hh"
-#include "attr-path.hh"
-#include "signals.hh"
-#include "store-api.hh"
-#include "log-store.hh"
-#include "common-eval-args.hh"
-#include "get-drvs.hh"
-#include "derivations.hh"
-#include "globals.hh"
-#include "flake/flake.hh"
-#include "flake/lockfile.hh"
-#include "users.hh"
-#include "editor-for.hh"
-#include "finally.hh"
-#include "markdown.hh"
-#include "local-fs-store.hh"
-#include "print.hh"
-#include "ref.hh"
-#include "value.hh"
+#include "nix/ansicolor.hh"
+#include "nix/shared.hh"
+#include "nix/eval.hh"
+#include "nix/eval-settings.hh"
+#include "nix/attr-path.hh"
+#include "nix/signals.hh"
+#include "nix/store-api.hh"
+#include "nix/log-store.hh"
+#include "nix/common-eval-args.hh"
+#include "nix/get-drvs.hh"
+#include "nix/derivations.hh"
+#include "nix/globals.hh"
+#include "nix/flake/flake.hh"
+#include "nix/flake/lockfile.hh"
+#include "nix/users.hh"
+#include "nix/editor-for.hh"
+#include "nix/finally.hh"
+#include "nix/markdown.hh"
+#include "nix/local-fs-store.hh"
+#include "nix/print.hh"
+#include "nix/ref.hh"
+#include "nix/value.hh"
 
-#include "strings.hh"
+#include "nix/strings.hh"
 
 namespace nix {