From f14121f9bb88ae90b89cda2018613d404ab72c3a Mon Sep 17 00:00:00 2001
From: Solene Rapenne <solene.rapenne@tweag.io>
Date: Thu, 29 Sep 2022 18:12:53 +0200
Subject: [PATCH] bento: add command diff

---
 bento            | 43 ++++++++++++++++++++++++++++++++++++++++++-
 doc/how-to.md    | 28 ++++++++++++++++++++++++++++
 doc/reference.md |  7 +++++--
 3 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/bento b/bento
index ed1785d..608c965 100755
--- a/bento
+++ b/bento
@@ -5,7 +5,7 @@ TIMEOUT=20
 # FUNCTION LIBRARIES
 usage() {                                                                                    
     cat <<EOF
-usage: bento init | deploy | build [dry-run|test|switch] | status [delay] | flake-update [input]
+usage: bento init | deploy | diff | build [dry-run|test|switch] | status [delay] | flake-update [input]
 
 bento init
 : create the layout for bento in the current directory
@@ -13,6 +13,9 @@ bento init
 bento deploy
 : build configurations and deploy configuration files, require to be root
 
+bento diff
+: display the closures difference between the current and new system versions
+
 bento build [dry-run|test|switch]
 : build configurations, can activate (test or switch) a build locally
 
@@ -42,6 +45,35 @@ check_bento() {
     fi
 }
 
+version_diff() {
+    cd "${CHROOT_DIR}" || exit 5
+
+    for i in $1
+    do
+        test -d "${i}" || continue
+
+        # date calculation
+        LASTLOG=$(find "${i}/logs/" -type f | sort -n | tail -n 1)
+        LASTLOGVERSION="$(basename "$LASTLOG" | awk -F '_' '{ print $2 }' )"
+        EXPECTED_CONFIG="$(awk -F '=' -v host="${i}" 'host == $1 { print $2 }' states.txt)"
+
+        # we can't do anything for non-flakes systems
+        if [ -z "${EXPECTED_CONFIG}" ]; then continue ; fi
+
+        if [ -n "${LASTLOG}" ]
+        then
+            if [ ! "${LASTLOGVERSION}" = "${EXPECTED_CONFIG}" ]
+            then
+                echo "Changes in $i between ${LASTLOGVERSION} and ${EXPECTED_CONFIG}"
+                nix store diff-closures "/nix/store/${LASTLOGVERSION}" "/nix/store/${EXPECTED_CONFIG}"
+            else
+                echo "$i is running the latest version"
+            fi
+            echo "-------------"
+        fi
+    done
+}
+
 display_status() {
     cd "${CHROOT_DIR}" || exit 5
     PRETTY_OUT_COLUMN=$(ls -1 | awk '{ if(length($1) > max) { max = length($1) }} END { print max }')
@@ -731,4 +763,13 @@ then
     exit 0
 fi
 
+# show a diff of closures
+if [ "$1" = "diff" ]
+then
+    . ./config.sh
+    version_diff "$NAME"
+
+    exit 0
+fi
+
 usage
diff --git a/doc/how-to.md b/doc/how-to.md
index 96ee19d..be9a411 100644
--- a/doc/how-to.md
+++ b/doc/how-to.md
@@ -87,3 +87,31 @@ Using `bento status` you can track the current state of each hosts (time since l
 With `bento flake-update` you can easily update your flakes recursively to the latest version.
 
 A parameter can be added to only update a given source with, i.e to update all nixpkgs in the flakes `bento flake-update nixpkgs`.
+
+# Show differences between a running system version and its new version
+
+With `env NAME=my-laptop bento diff` you can display the differences of packages between what `my-laptop` is running and its new version.
+
+The output should look like this:
+
+```
+Changes in x1 between p50qql7f42rl0fccdwxw45k21pnqb9ii-nixos-system-x1-22.11.20220921.d6490a0 and 7zfxxddmg8l6qc6bksar5gm62ylwsdv5-nixos-system-x1-22.11.20220927.7e52b35
+bind: 9.18.6 → 9.18.7
+cpupower: 5.19.9, 5.19.9_fish → 5.19.11, 5.19.11_fish
+gh: 2.15.0, 2.15.0_fish → 2.16.1, 2.16.1_fish
+imagemagick: 7.1.0-48 → 7.1.0-49, +18.0 KiB
+initrd-linux: 5.19.9 → 5.19.11
+libblockdev: 2.26 → 2.28
+libbytesize: 2.6 → 2.7
+libdmtx: 0.7.5 → 0.7.7
+linux: 5.19.9, 5.19.9-modules → 5.19.11, 5.19.11-modules, +126.6 KiB
+man: -11.8 KiB
+nixos: +12.5 KiB
+nixos-system-x1: 22.11.20220921.d6490a0 → 22.11.20220927.7e52b35
+opencv: 4.5.4 → 4.6.0, +1901.6 KiB
+plasma-workspace: +62.4 KiB
+root-authorized_keys: ∅ → ε
+source: +701.9 KiB
+systemsettings: +62.6 KiB
+-------------
+```
diff --git a/doc/reference.md b/doc/reference.md
index 8eb561b..70e76ab 100644
--- a/doc/reference.md
+++ b/doc/reference.md
@@ -4,7 +4,10 @@
   - create the layout for bento in the current directory (only work from flakes)
 
 - `bento deploy`
-  - build configurations and deploy configuration files, requires to be root
+  - build configurations and deploy configuration files, requires to be root.
+
+- `bento diff`
+  - display the difference between each remote system version and their new version. Supports `NAME` environment variable.
 
 - `bento build [dry-run|build|test|switch]`
   - dry-build or build configurations. Using `test` or `switch`, can be used to apply a configuration locally. Default is `build`.
@@ -31,7 +34,7 @@ A local file `config.sh` is required for Bento, it contains variable used to gen
 
 `bento` is using the following environment variables as configuration:
 - `BENTO_DIR`: contains the path of a bento directory, so you can run `bento` commands from anywhere
-- `NAME`: contains machine names (flake config or directory in `hosts/`) to restrict commands `deploy` and `build` to this machine only
+- `NAME`: contains machine names (flake config or directory in `hosts/`) to restrict commands `deploy`, `diff` and `build` to this machine only
 - `VERBOSE`: if defined to anything, display `nixos-rebuild` output for local builds done with `bento build` or `bento deploy`
 
 # Self update mode