Merge pull request #4803 from ShamrockLee/nix-channel-list-generations

Add `nix-channel --list-generations`

doc/manual/src/command-ref/nix-channel.md

@@ -4,7 +4,7 @@
 
 # Synopsis
 
-`nix-channel` {`--add` url [*name*] | `--remove` *name* | `--list` | `--update` [*names…*] | `--rollback` [*generation*] }
+`nix-channel` {`--add` url [*name*] | `--remove` *name* | `--list` | `--update` [*names…*] | `--list-generations` | `--rollback` [*generation*] }
 
 # Description
 
@@ -39,6 +39,15 @@ This command has the following operations:
     for `nix-env` operations (by symlinking them from the directory
     `~/.nix-defexpr`).
 
+  - `--list-generations`\
+    Prints a list of all the current existing generations for the
+    channel profile.
+
+    Works the same way as
+    ```
+    nix-env --profile /nix/var/nix/profiles/per-user/$USER/channels --list-generations
+    ```
+
   - `--rollback` \[*generation*\]\
     Reverts the previous call to `nix-channel
                     --update`. Optionally, you can specify a specific channel generation

doc/manual/src/release-notes/rl-next.md

@@ -1,2 +1,3 @@
 # Release X.Y (202?-??-??)
 
+- [`nix-channel`](../command-ref/nix-channel.md) now supports a `--list-generations` subcommand

src/nix-channel/nix-channel.cc

@@ -177,6 +177,7 @@ static int main_nix_channel(int argc, char ** argv)
             cRemove,
             cList,
             cUpdate,
+            cListGenerations,
             cRollback
         } cmd = cNone;
         std::vector<std::string> args;
@@ -193,6 +194,8 @@ static int main_nix_channel(int argc, char ** argv)
                 cmd = cList;
             } else if (*arg == "--update") {
                 cmd = cUpdate;
+            } else if (*arg == "--list-generations") {
+                cmd = cListGenerations;
             } else if (*arg == "--rollback") {
                 cmd = cRollback;
             } else {
@@ -237,6 +240,11 @@ static int main_nix_channel(int argc, char ** argv)
             case cUpdate:
                 update(StringSet(args.begin(), args.end()));
                 break;
+            case cListGenerations:
+                if (!args.empty())
+                    throw UsageError("'--list-generations' expects no arguments");
+                std::cout << runProgram(settings.nixBinDir + "/nix-env", false, {"--profile", profile, "--list-generations"}) << std::flush;
+                break;
             case cRollback:
                 if (args.size() > 1)
                     throw UsageError("'--rollback' has at most one argument");

tests/nix-channel.sh

@@ -8,6 +8,7 @@ rm -f $TEST_HOME/.nix-channels $TEST_HOME/.nix-profile
 nix-channel --add http://foo/bar xyzzy
 nix-channel --list | grepQuiet http://foo/bar
 nix-channel --remove xyzzy
+[[ $(nix-channel --list-generations | wc -l) == 1 ]]
 
 [ -e $TEST_HOME/.nix-channels ]
 [ "$(cat $TEST_HOME/.nix-channels)" = '' ]
@@ -38,6 +39,7 @@ ln -s dependencies.nix $TEST_ROOT/nixexprs/default.nix
 # Test the update action.
 nix-channel --add file://$TEST_ROOT/foo
 nix-channel --update
+[[ $(nix-channel --list-generations | wc -l) == 2 ]]
 
 # Do a query.
 nix-env -qa \* --meta --xml --out-path > $TEST_ROOT/meta.xml