tortoisehg: untie from mercurial and update to 5.0.2 (#66173)

* tortoisehg: untie from mercurial

When I've added `tortoisehg` package, it turned out that mercurial updates
sometimes broke thg. I've added a comment to `mercurial/default.nix` to
update torotisehg version during mercurial updates, but this worked the other way round:
mercurial stopped to be updated regularly (#60993).

And sadly it didn't solve the issue - #61759.

Here I'm trying to untie them. Tortoisehg will build a custom mercurial package
if versions don't match. This makes updating tortoisehg more complicated,
but it is still better than current situation.

* expose custom mercurial from thg package

pkgs/applications/version-management/mercurial/default.nix

@@ -1,20 +1,23 @@
 { stdenv, fetchurl, python2Packages, makeWrapper, unzip
 , guiSupport ? false, tk ? null
-, ApplicationServices }:
+, ApplicationServices
+, mercurialSrc ? fetchurl rec {
+    meta.name = "mercurial-${meta.version}";
+    meta.version = "4.9.1";
+    url = "https://mercurial-scm.org/release/${meta.name}.tar.gz";
+    sha256 = "0iybbkd9add066729zg01kwz5hhc1s6lhp9rrnsmzq6ihyxj3p8v";
+  }
+}:
 
 let
-  # if you bump version, update pkgs.tortoisehg too or ping maintainer
-  version = "4.9.1";
-  name = "mercurial-${version}";
   inherit (python2Packages) docutils hg-git dulwich python;
+
 in python2Packages.buildPythonApplication {
-  inherit name;
-  format = "other";
 
-  src = fetchurl {
-    url = "https://mercurial-scm.org/release/${name}.tar.gz";
-    sha256 = "0iybbkd9add066729zg01kwz5hhc1s6lhp9rrnsmzq6ihyxj3p8v";
-  };
+  inherit (mercurialSrc.meta) name version;
+  src = mercurialSrc;
+
+  format = "other";
 
   inherit python; # pass it so that the same version can be used in hg2git
 
@@ -55,7 +58,7 @@ in python2Packages.buildPythonApplication {
     '';
 
   meta = {
-    inherit version;
+    inherit (mercurialSrc.meta) version;
     description = "A fast, lightweight SCM system for very large distributed projects";
     homepage = https://www.mercurial-scm.org;
     downloadPage = https://www.mercurial-scm.org/release/;

pkgs/applications/version-management/tortoisehg/default.nix

@@ -1,13 +1,30 @@
-{lib, fetchurl, mercurial, python2Packages}:
+{ lib, fetchurl, python2Packages
+, mercurial
+}@args:
+let
+  tortoisehgSrc = fetchurl rec {
+    meta.name = "tortoisehg-${meta.version}";
+    meta.version = "5.0.2";
+    url = "https://bitbucket.org/tortoisehg/targz/downloads/${meta.name}.tar.gz";
+    sha256 = "1fkawx4ymaacah2wpv2w7rxmv1mx08mg4x4r4fxh41jz1njjb8sz";
+  };
 
-python2Packages.buildPythonApplication rec {
-    name = "tortoisehg-${version}";
-    version = "5.0.2";
+  mercurial =
+    if args.mercurial.meta.version == tortoisehgSrc.meta.version
+      then args.mercurial
+      else args.mercurial.override {
+        mercurialSrc = fetchurl rec {
+          meta.name = "mercurial-${meta.version}";
+          meta.version = tortoisehgSrc.meta.version;
+          url = "https://mercurial-scm.org/release/${meta.name}.tar.gz";
+          sha256 = "1y60hfc8gh4ha9sw650qs7hndqmvbn0qxpmqwpn4q18z5xwm1f19";
+        };
+      };
 
-    src = fetchurl {
-      url = "https://bitbucket.org/tortoisehg/targz/downloads/${name}.tar.gz";
-      sha256 = "1fkawx4ymaacah2wpv2w7rxmv1mx08mg4x4r4fxh41jz1njjb8sz";
-    };
+in python2Packages.buildPythonApplication rec {
+
+    inherit (tortoisehgSrc.meta) name version;
+    src = tortoisehgSrc;
 
     pythonPath = with python2Packages; [ pyqt4 mercurial qscintilla iniparse ];
 
@@ -28,6 +45,8 @@ python2Packages.buildPythonApplication rec {
       $out/bin/thg version
     '';
 
+    passthru.mercurial = mercurial;
+
     meta = {
       description = "Qt based graphical tool for working with Mercurial";
       homepage = https://tortoisehg.bitbucket.io/;