1 files changed, 85 insertions, 0 deletions
diff --git a/home-manager/modules/lib-bash/activation-init.sh b/home-manager/modules/lib-bash/activation-init.sh
new file mode 100755
index 00000000000..f95008ee75b
--- /dev/null
+++ b/home-manager/modules/lib-bash/activation-init.sh
@@ -0,0 +1,85 @@
+#!/usr/bin/env bash
+
+function setupVars() {
+    local nixStateDir="${NIX_STATE_DIR:-/nix/var/nix}"
+    local profilesPath="$nixStateDir/profiles/per-user/$USER"
+    local gcPath="$nixStateDir/gcroots/per-user/$USER"
+
+    genProfilePath="$profilesPath/home-manager"
+    newGenPath="@GENERATION_DIR@";
+    newGenGcPath="$gcPath/current-home"
+
+    local greatestGenNum
+    greatestGenNum=$( \
+        nix-env --list-generations --profile "$genProfilePath" \
+            | tail -1 \
+            | sed -E 's/ *([[:digit:]]+) .*/\1/')
+
+    if [[ -n $greatestGenNum ]] ; then
+        oldGenNum=$greatestGenNum
+        newGenNum=$((oldGenNum + 1))
+    else
+        newGenNum=1
+    fi
+
+    if [[ -e $profilesPath/home-manager ]] ; then
+        oldGenPath="$(readlink -e "$profilesPath/home-manager")"
+    fi
+
+    $VERBOSE_ECHO "Sanity checking oldGenNum and oldGenPath"
+    if [[ -v oldGenNum && ! -v oldGenPath
+            || ! -v oldGenNum && -v oldGenPath ]]; then
+        errorEcho "Invalid profile number and current profile values! These"
+        errorEcho "must be either both empty or both set but are now set to"
+        errorEcho "    '${oldGenNum:-}' and '${oldGenPath:-}'"
+        errorEcho "If you don't mind losing previous profile generations then"
+        errorEcho "the easiest solution is probably to run"
+        errorEcho "   rm $profilesPath/home-manager*"
+        errorEcho "   rm $gcPath/current-home"
+        errorEcho "and trying home-manager switch again. Good luck!"
+        exit 1
+    fi
+}
+
+if [[ -v VERBOSE ]]; then
+    export VERBOSE_ECHO=echo
+    export VERBOSE_ARG="--verbose"
+else
+    export VERBOSE_ECHO=true
+    export VERBOSE_ARG=""
+fi
+
+echo "Starting home manager activation"
+
+# Verify that we can connect to the Nix store and/or daemon. This will
+# also create the necessary directories in profiles and gcroots.
+$VERBOSE_ECHO "Sanity checking Nix"
+nix-build --expr '{}' --no-out-link
+
+setupVars
+
+if [[ -v DRY_RUN ]] ; then
+    echo "This is a dry run"
+    export DRY_RUN_CMD=echo
+else
+    $VERBOSE_ECHO "This is a live run"
+    export DRY_RUN_CMD=""
+fi
+
+if [[ -v VERBOSE ]]; then
+    echo -n "Using Nix version: "
+    nix-env --version
+fi
+
+$VERBOSE_ECHO "Activation variables:"
+if [[ -v oldGenNum ]] ; then
+    $VERBOSE_ECHO "  oldGenNum=$oldGenNum"
+    $VERBOSE_ECHO "  oldGenPath=$oldGenPath"
+else
+    $VERBOSE_ECHO "  oldGenNum undefined (first run?)"
+    $VERBOSE_ECHO "  oldGenPath undefined (first run?)"
+fi
+$VERBOSE_ECHO "  newGenPath=$newGenPath"
+$VERBOSE_ECHO "  newGenNum=$newGenNum"
+$VERBOSE_ECHO "  newGenGcPath=$newGenGcPath"
+$VERBOSE_ECHO "  genProfilePath=$genProfilePath"