Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/libexpr/eval-settings.cc

@@ -0,0 +1,106 @@
+#include "users.hh"
+#include "globals.hh"
+#include "profiles.hh"
+#include "eval.hh"
+#include "eval-settings.hh"
+
+namespace nix {
+
+/* Very hacky way to parse $NIX_PATH, which is colon-separated, but
+   can contain URLs (e.g. "nixpkgs=https://bla...:foo=https://"). */
+Strings EvalSettings::parseNixPath(const std::string & s)
+{
+    Strings res;
+
+    auto p = s.begin();
+
+    while (p != s.end()) {
+        auto start = p;
+        auto start2 = p;
+
+        while (p != s.end() && *p != ':') {
+            if (*p == '=') start2 = p + 1;
+            ++p;
+        }
+
+        if (p == s.end()) {
+            if (p != start) res.push_back(std::string(start, p));
+            break;
+        }
+
+        if (*p == ':') {
+            auto prefix = std::string(start2, s.end());
+            if (EvalSettings::isPseudoUrl(prefix) || hasPrefix(prefix, "flake:")) {
+                ++p;
+                while (p != s.end() && *p != ':') ++p;
+            }
+            res.push_back(std::string(start, p));
+            if (p == s.end()) break;
+        }
+
+        ++p;
+    }
+
+    return res;
+}
+
+EvalSettings::EvalSettings(bool & readOnlyMode, EvalSettings::LookupPathHooks lookupPathHooks)
+    : readOnlyMode{readOnlyMode}
+    , lookupPathHooks{lookupPathHooks}
+{
+    auto var = getEnv("NIX_ABORT_ON_WARN");
+    if (var && (var == "1" || var == "yes" || var == "true"))
+        builtinsAbortOnWarn = true;
+}
+
+Strings EvalSettings::getDefaultNixPath()
+{
+    Strings res;
+    auto add = [&](const Path & p, const std::string & s = std::string()) {
+        if (pathAccessible(p)) {
+            if (s.empty()) {
+                res.push_back(p);
+            } else {
+                res.push_back(s + "=" + p);
+            }
+        }
+    };
+
+    add(getNixDefExpr() + "/channels");
+    add(rootChannelsDir() + "/nixpkgs", "nixpkgs");
+    add(rootChannelsDir());
+
+    return res;
+}
+
+bool EvalSettings::isPseudoUrl(std::string_view s)
+{
+    if (s.compare(0, 8, "channel:") == 0) return true;
+    size_t pos = s.find("://");
+    if (pos == std::string::npos) return false;
+    std::string scheme(s, 0, pos);
+    return scheme == "http" || scheme == "https" || scheme == "file" || scheme == "channel" || scheme == "git" || scheme == "s3" || scheme == "ssh";
+}
+
+std::string EvalSettings::resolvePseudoUrl(std::string_view url)
+{
+    if (hasPrefix(url, "channel:"))
+        return "https://nixos.org/channels/" + std::string(url.substr(8)) + "/nixexprs.tar.xz";
+    else
+        return std::string(url);
+}
+
+const std::string & EvalSettings::getCurrentSystem() const
+{
+    const auto & evalSystem = currentSystem.get();
+    return evalSystem != "" ? evalSystem : settings.thisSystem.get();
+}
+
+Path getNixDefExpr()
+{
+    return settings.useXDGBaseDirectories
+        ? getStateDir() + "/defexpr"
+        : getHome() + "/.nix-defexpr";
+}
+
+}