From 89c1d2b202dccbf91c40586ac33efee515f7e93d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Fri, 27 Apr 2007 23:48:14 +0000
Subject: [PATCH] * Package flag "keep" that prevents a package from being
 removed from   a user environment by an install or upgrade action.  This is  
 particularly useful if you have a version installed that you don't   want to
 upgrade (e.g., because the newer versions are broken).   Example:

    $ nix-env -u zapping --dry-run
    (dry run; not doing anything)
    upgrading `zapping-0.9.6' to `zapping-0.10cvs6'

    $ nix-env --set-flag keep true zapping

    $ nix-env -u zapping --dry-run
    (dry run; not doing anything)

  However, "-e" will still uninstall the package.  (Maybe we should
  require the keep flag to be explicitly set to false before it can be
  uninstalled.)
---
 doc/manual/release-notes.xml | 4 ++--
 src/nix-env/nix-env.cc       | 7 ++++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/doc/manual/release-notes.xml b/doc/manual/release-notes.xml
index 161643e52d..3b4525129d 100644
--- a/doc/manual/release-notes.xml
+++ b/doc/manual/release-notes.xml
@@ -72,8 +72,8 @@
 
   <listitem><para>TODO: <command>nix-env</command>
   <option>--set-flag</option>.  Specific flags:
-  <literal>active</literal>,
-  <literal>priority</literal>.</para></listitem>
+  <literal>active</literal>, <literal>priority</literal>,
+  <literal>keep</literal>.</para></listitem>
   
 
   <listitem><para><command>nix-env -q</command> now has a flag
diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index 77b7881711..1a4d8ee587 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -482,8 +482,10 @@ static void installDerivations(Globals & globals,
          i != installedElems.end(); ++i)
     {
         DrvName drvName(i->name);
+        MetaInfo meta = i->queryMetaInfo(globals.state);
         if (!globals.preserveInstalled &&
-            newNames.find(drvName.name) != newNames.end())
+            newNames.find(drvName.name) != newNames.end() &&
+            meta["keep"] == "true")
             printMsg(lvlInfo,
                 format("replacing old `%1%'") % i->name);
         else
@@ -543,6 +545,9 @@ static void upgradeDerivations(Globals & globals,
     {
         DrvName drvName(i->name);
 
+        MetaInfo meta = i->queryMetaInfo(globals.state);
+        if (meta["keep"] == "true") continue;
+
         /* Find the derivation in the input Nix expression with the
            same name and satisfying the version constraints specified
            by upgradeType.  If there are multiple matches, take the