revsets: add branches() and tags() functions

The `branches()` function resolves to all "adds" on both local and
remote branches.

README.md

@@ -243,11 +243,11 @@ By default, `jj log` lists all revisions (commits) in the repo that have not
 been rewritten (roughly speaking). We can use the `-r` flag to restrict which
 revisions we want to list. The flag accepts a "revset", which is an expression
 in a simple language for specifying revision. For example, `@` refers to the
-working copy commit, `root` refers to the root commit, `git_refs()` refers to
-all commits pointed to by git refs. We can combine expression with `|` for
+working copy commit, `root` refers to the root commit, `branches()` refers to
+all commits pointed to by branches. We can combine expression with `|` for
 union, `&` for intersection and `-` for difference. For example:
 ```shell script
-$ jj log -r '@ | root | git_refs()'
+$ jj log -r '@ | root | branches()'
 @ 192b456b024b f39aeb1a0200 martinvonz@google.com 2021-05-23 23:10:27.000 -07:00
 :
 o 080a9b37ff7e 6a91b4ba16c7 martinvonz@google.com 2021-05-23 22:08:37.000 -07:00 main

lib/src/revset.rs

@@ -192,6 +192,8 @@ pub enum RevsetExpression {
     },
     AllHeads,
     PublicHeads,
+    Branches,
+    Tags,
     GitRefs,
     NonObsoleteHeads(Rc<RevsetExpression>),
     ParentCount {
@@ -495,6 +497,26 @@ fn parse_function_expression(
                 })
             }
         }
+        "branches" => {
+            if arg_count == 0 {
+                Ok(RevsetExpression::Branches)
+            } else {
+                Err(RevsetParseError::InvalidFunctionArguments {
+                    name,
+                    message: "Expected 0 arguments".to_string(),
+                })
+            }
+        }
+        "tags" => {
+            if arg_count == 0 {
+                Ok(RevsetExpression::Tags)
+            } else {
+                Err(RevsetParseError::InvalidFunctionArguments {
+                    name,
+                    message: "Expected 0 arguments".to_string(),
+                })
+            }
+        }
         "git_refs" => {
             if arg_count == 0 {
                 Ok(RevsetExpression::GitRefs)
@@ -969,6 +991,37 @@ pub fn evaluate_expression<'repo>(
             index_entries.sort_by_key(|b| Reverse(b.position()));
             Ok(Box::new(EagerRevset { index_entries }))
         }
+        RevsetExpression::Branches => {
+            let index = repo.index();
+            let mut index_entries = vec![];
+            for branch_target in repo.view().branches().values() {
+                if let Some(local_target) = &branch_target.local_target {
+                    for id in local_target.adds() {
+                        index_entries.push(index.entry_by_id(&id).unwrap());
+                    }
+                }
+                for remote_target in branch_target.remote_targets.values() {
+                    for id in remote_target.adds() {
+                        index_entries.push(index.entry_by_id(&id).unwrap());
+                    }
+                }
+            }
+            index_entries.sort_by_key(|b| Reverse(b.position()));
+            index_entries.dedup();
+            Ok(Box::new(EagerRevset { index_entries }))
+        }
+        RevsetExpression::Tags => {
+            let index = repo.index();
+            let mut index_entries = vec![];
+            for ref_target in repo.view().tags().values() {
+                for id in ref_target.adds() {
+                    index_entries.push(index.entry_by_id(&id).unwrap());
+                }
+            }
+            index_entries.sort_by_key(|b| Reverse(b.position()));
+            index_entries.dedup();
+            Ok(Box::new(EagerRevset { index_entries }))
+        }
         RevsetExpression::GitRefs => {
             let index = repo.index();
             let mut index_entries = vec![];