allow pulling <project>/releases/latest

parser-typechecker/src/Unison/Codebase/Editor/RemoteRepo.hs

@@ -111,7 +111,7 @@ data ReadRemoteNamespace a
   | -- | A remote project+branch, specified by name (e.g. @unison/base/main).
     -- Currently assumed to be hosted on Share, though we could include a ShareCodeserver in here, too.
     ReadShare'ProjectBranch !a
-  deriving stock (Eq, Show, Generic)
+  deriving stock (Eq, Functor, Show, Generic)
 
 data ReadGitRemoteNamespace = ReadGitRemoteNamespace
   { repo :: !ReadGitRepo,

unison-cli/package.yaml

@@ -68,6 +68,7 @@ dependencies:
   - text-builder
   - text-rope
   - these
+  - these-lens
   - time
   - transformers
   - unison-codebase
@@ -188,6 +189,7 @@ default-extensions:
   - GeneralizedNewtypeDeriving
   - ImportQualifiedPost
   - InstanceSigs
+  - KindSignatures
   - LambdaCase
   - MultiParamTypeClasses
   - MultiWayIf

unison-cli/src/Unison/Codebase/Editor/HandleInput.hs

@@ -150,6 +150,7 @@ import Unison.PrettyPrintEnv.Names qualified as PPE
 import Unison.PrettyPrintEnvDecl qualified as PPE hiding (biasTo, empty)
 import Unison.PrettyPrintEnvDecl qualified as PPED
 import Unison.PrettyPrintEnvDecl.Names qualified as PPED
+import Unison.Project (ProjectBranchNameOrLatestRelease (..))
 import Unison.Reference (Reference (..), TermReference)
 import Unison.Reference qualified as Reference
 import Unison.Referent (Referent)
@@ -2466,8 +2467,8 @@ doFetchCompiler username branch =
     -- fetching info
     prj =
       These
-        (unsafeFrom $ "@" <> Text.pack username <> "/internal")
-        (unsafeFrom $ Text.pack branch)
+        (unsafeFrom @Text $ "@" <> Text.pack username <> "/internal")
+        (ProjectBranchNameOrLatestRelease'Name . unsafeFrom @Text $ Text.pack branch)
 
     sourceTarget =
       PullSourceTarget2

unison-cli/src/Unison/Codebase/Editor/HandleInput/Pull.hs

@@ -49,9 +49,10 @@ import Unison.Codebase.SyncMode qualified as SyncMode
 import Unison.Codebase.Verbosity qualified as Verbosity
 import Unison.CommandLine.InputPattern qualified as InputPattern
 import Unison.CommandLine.InputPatterns qualified as InputPatterns
+import Unison.Core.Project (ProjectBranchName (UnsafeProjectBranchName))
 import Unison.NameSegment (NameSegment (..))
 import Unison.Prelude
-import Unison.Project (ProjectAndBranch (..), ProjectBranchName, ProjectName)
+import Unison.Project (ProjectAndBranch (..), ProjectBranchNameOrLatestRelease (..), ProjectName)
 import Unison.Share.API.Hash qualified as Share
 import Unison.Share.Codeserver qualified as Codeserver
 import Unison.Share.Sync qualified as Share
@@ -59,6 +60,7 @@ import Unison.Share.Sync.Types qualified as Share
 import Unison.Share.Types (codeserverBaseURL)
 import Unison.Sync.Common qualified as Common
 import Unison.Sync.Types qualified as Share
+import Witch (unsafeFrom)
 
 doPullRemoteBranch :: PullSourceTarget -> SyncMode.SyncMode -> PullMode -> Verbosity.Verbosity -> Cli ()
 doPullRemoteBranch unresolvedSourceAndTarget syncMode pullMode verbosity = do
@@ -151,13 +153,53 @@ resolveImplicitSource =
       pure (ReadShare'ProjectBranch remoteBranch)
 
 resolveExplicitSource ::
-  ReadRemoteNamespace (These ProjectName ProjectBranchName) ->
+  ReadRemoteNamespace (These ProjectName ProjectBranchNameOrLatestRelease) ->
   Cli (ReadRemoteNamespace Share.RemoteProjectBranch)
 resolveExplicitSource = \case
   ReadRemoteNamespaceGit namespace -> pure (ReadRemoteNamespaceGit namespace)
   ReadShare'LooseCode namespace -> pure (ReadShare'LooseCode namespace)
-  ReadShare'ProjectBranch projectAndBranchNames ->
-    ReadShare'ProjectBranch <$> ProjectUtils.expectRemoteProjectBranchByTheseNames projectAndBranchNames
+  ReadShare'ProjectBranch (This remoteProjectName) -> do
+    remoteProject <- ProjectUtils.expectRemoteProjectByName remoteProjectName
+    let remoteProjectId = remoteProject ^. #projectId
+    let remoteBranchName = unsafeFrom @Text "main"
+    remoteProjectBranch <-
+      ProjectUtils.expectRemoteProjectBranchByName
+        (ProjectAndBranch (remoteProjectId, remoteProjectName) remoteBranchName)
+    pure (ReadShare'ProjectBranch remoteProjectBranch)
+  ReadShare'ProjectBranch (That branchNameOrLatestRelease) -> do
+    (ProjectAndBranch localProject localBranch, _restPath) <- ProjectUtils.expectCurrentProjectBranch
+    let localProjectId = localProject ^. #projectId
+    let localBranchId = localBranch ^. #branchId
+    Cli.runTransaction (Queries.loadRemoteProjectBranch localProjectId Share.hardCodedUri localBranchId) >>= \case
+      Just (remoteProjectId, _maybeProjectBranchId) -> do
+        remoteProjectName <- Cli.runTransaction (Queries.expectRemoteProjectName remoteProjectId Share.hardCodedUri)
+        remoteBranchName <- resolveRemoteBranchName remoteProjectName branchNameOrLatestRelease
+        remoteProjectBranch <-
+          ProjectUtils.expectRemoteProjectBranchByName
+            (ProjectAndBranch (remoteProjectId, remoteProjectName) remoteBranchName)
+        pure (ReadShare'ProjectBranch remoteProjectBranch)
+      Nothing -> do
+        Cli.returnEarly $
+          Output.NoAssociatedRemoteProject
+            Share.hardCodedUri
+            (ProjectAndBranch (localProject ^. #name) (localBranch ^. #name))
+  ReadShare'ProjectBranch (These projectName branchNameOrLatestRelease) -> do
+    remoteProject <- ProjectUtils.expectRemoteProjectByName projectName
+    let remoteProjectId = remoteProject ^. #projectId
+    branchName <- resolveRemoteBranchName projectName branchNameOrLatestRelease
+    remoteProjectBranch <-
+      ProjectUtils.expectRemoteProjectBranchByName
+        (ProjectAndBranch (remoteProjectId, projectName) branchName)
+    pure (ReadShare'ProjectBranch remoteProjectBranch)
+  where
+    resolveRemoteBranchName :: ProjectName -> ProjectBranchNameOrLatestRelease -> Cli ProjectBranchName
+    resolveRemoteBranchName projectName = \case
+      ProjectBranchNameOrLatestRelease'Name branchName -> pure branchName
+      ProjectBranchNameOrLatestRelease'LatestRelease -> do
+        remoteProject <- ProjectUtils.expectRemoteProjectByName projectName
+        case remoteProject ^. #latestRelease of
+          Nothing -> Cli.returnEarly (Output.ProjectHasNoReleases projectName)
+          Just semver -> pure (UnsafeProjectBranchName ("releases/" <> into @Text semver))
 
 resolveImplicitTarget :: Cli (Either Path' (ProjectAndBranch Sqlite.Project Sqlite.ProjectBranch))
 resolveImplicitTarget =

unison-cli/src/Unison/Codebase/Editor/Input.hs

@@ -45,7 +45,7 @@ import Unison.HashQualified qualified as HQ
 import Unison.Name (Name)
 import Unison.NameSegment (NameSegment)
 import Unison.Prelude
-import Unison.Project (ProjectAndBranch, ProjectAndBranchNames, ProjectBranchName, ProjectName, Semver)
+import Unison.Project (ProjectAndBranch, ProjectAndBranchNames, ProjectBranchName, ProjectName, Semver, ProjectBranchNameOrLatestRelease)
 import Unison.ShortHash (ShortHash)
 import Unison.Util.Pretty qualified as P
 
@@ -268,8 +268,8 @@ data GistInput = GistInput
 -- | Pull source and target: either neither is specified, or only a source, or both.
 data PullSourceTarget
   = PullSourceTarget0
-  | PullSourceTarget1 (ReadRemoteNamespace (These ProjectName ProjectBranchName))
-  | PullSourceTarget2 (ReadRemoteNamespace (These ProjectName ProjectBranchName)) LooseCodeOrProject
+  | PullSourceTarget1 (ReadRemoteNamespace (These ProjectName ProjectBranchNameOrLatestRelease))
+  | PullSourceTarget2 (ReadRemoteNamespace (These ProjectName ProjectBranchNameOrLatestRelease)) LooseCodeOrProject
   deriving stock (Eq, Show)
 
 data PushSource

unison-cli/src/Unison/Codebase/Editor/Output.hs

@@ -382,6 +382,7 @@ data Output
   | FetchingLatestReleaseOfBase
   | FailedToFetchLatestReleaseOfBase
   | HappyCoding
+  | ProjectHasNoReleases ProjectName
 
 -- | What did we create a project branch from?
 --
@@ -603,6 +604,7 @@ isFailure o = case o of
   FetchingLatestReleaseOfBase {} -> False
   FailedToFetchLatestReleaseOfBase {} -> True
   HappyCoding {} -> False
+  ProjectHasNoReleases {} -> True
 
 isNumberedFailure :: NumberedOutput -> Bool
 isNumberedFailure = \case

unison-cli/src/Unison/Codebase/Editor/UriParser.hs

@@ -1,10 +1,9 @@
 module Unison.Codebase.Editor.UriParser
-  ( repoPath,
+  ( readRemoteNamespaceParser,
     writeGitRepo,
     deprecatedWriteGitRemoteNamespace,
     writeRemoteNamespace,
     writeRemoteNamespaceWith,
-    parseReadRemoteNamespace,
     parseReadShareLooseCode,
   )
 where
@@ -34,7 +33,7 @@ import Unison.Codebase.Path qualified as Path
 import Unison.Codebase.ShortCausalHash (ShortCausalHash (..))
 import Unison.NameSegment (NameSegment (..))
 import Unison.Prelude
-import Unison.Project (ProjectBranchName, ProjectName, projectAndBranchNamesParser)
+import Unison.Project (ProjectBranchName, ProjectBranchSpecifier (..), ProjectName, projectAndBranchNamesParser)
 import Unison.Syntax.Lexer qualified
 import Unison.Util.Pretty qualified as P
 import Unison.Util.Pretty.MegaParsec qualified as P
@@ -59,29 +58,23 @@ type P = P.Parsec Void Text.Text
 
 -- $ git clone [user@]server:project.git[:treeish][:[#hash][.path]]
 
-repoPath :: P (ReadRemoteNamespace (These ProjectName ProjectBranchName))
-repoPath =
+readRemoteNamespaceParser :: ProjectBranchSpecifier branch -> P (ReadRemoteNamespace (These ProjectName branch))
+readRemoteNamespaceParser specifier =
   P.label "generic repo" $
     ReadRemoteNamespaceGit <$> readGitRemoteNamespace
-      <|> ReadShare'ProjectBranch <$> projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths
+      <|> ReadShare'ProjectBranch <$> projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths specifier
       <|> ReadShare'LooseCode <$> readShareLooseCode
 
-projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths :: P (These ProjectName ProjectBranchName)
-projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths =
+projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths ::
+  ProjectBranchSpecifier branch ->
+  P (These ProjectName branch)
+projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths specifier =
   P.try do
-    projectAndBranch <- projectAndBranchNamesParser
+    projectAndBranch <- projectAndBranchNamesParser specifier
     -- we don't want to succeed parsing the 'foo' off of 'foo.bar', leaving '.bar' behind
     P.notFollowedBy (C.char '.')
     pure projectAndBranch
 
-parseReadRemoteNamespace ::
-  String ->
-  String ->
-  Either (P.Pretty P.ColorText) (ReadRemoteNamespace (These ProjectName ProjectBranchName))
-parseReadRemoteNamespace label input =
-  let printError err = P.lines [P.string "I couldn't parse the repository address given above.", P.prettyPrintParseError input err]
-   in first printError (P.parse repoPath label (Text.pack input))
-
 parseReadShareLooseCode :: String -> String -> Either (P.Pretty P.ColorText) ReadShareLooseCode
 parseReadShareLooseCode label input =
   let printError err = P.lines [P.string "I couldn't parse this as a share path.", P.prettyPrintParseError input err]
@@ -93,7 +86,8 @@ parseReadShareLooseCode label input =
 -- Just (WriteRemoteNamespaceGit (WriteGitRemoteNamespace {repo = WriteGitRepo {url = "git@github.com:unisonweb/base", branch = Just "v3"}, path = _releases.M3}))
 writeRemoteNamespace :: P (WriteRemoteNamespace (These ProjectName ProjectBranchName))
 writeRemoteNamespace =
-  writeRemoteNamespaceWith projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths
+  writeRemoteNamespaceWith
+    (projectAndBranchNamesParserInTheContextOfAlsoParsingLooseCodePaths ProjectBranchSpecifier'Name)
 
 writeRemoteNamespaceWith :: P a -> P (WriteRemoteNamespace a)
 writeRemoteNamespaceWith projectBranchParser =

unison-cli/src/Unison/CommandLine/InputPatterns.hs

@@ -31,9 +31,9 @@ import Unison.Codebase.Editor.Input (DeleteOutput (..), DeleteTarget (..), Input
 import Unison.Codebase.Editor.Input qualified as Input
 import Unison.Codebase.Editor.Output.PushPull (PushPull (Pull, Push))
 import Unison.Codebase.Editor.Output.PushPull qualified as PushPull
-import Unison.Codebase.Editor.RemoteRepo (WriteGitRepo, WriteRemoteNamespace)
+import Unison.Codebase.Editor.RemoteRepo (ReadRemoteNamespace, WriteGitRepo, WriteRemoteNamespace)
 import Unison.Codebase.Editor.SlurpResult qualified as SR
-import Unison.Codebase.Editor.UriParser (parseReadRemoteNamespace)
+import Unison.Codebase.Editor.UriParser (readRemoteNamespaceParser)
 import Unison.Codebase.Editor.UriParser qualified as UriParser
 import Unison.Codebase.Path qualified as Path
 import Unison.Codebase.Path.Parse qualified as Path
@@ -51,7 +51,7 @@ import Unison.JitInfo qualified as JitInfo
 import Unison.Name (Name)
 import Unison.NameSegment qualified as NameSegment
 import Unison.Prelude
-import Unison.Project (ProjectAndBranch (..), ProjectAndBranchNames (..), ProjectBranchName, ProjectName, Semver)
+import Unison.Project (ProjectAndBranch (..), ProjectAndBranchNames (..), ProjectBranchName, ProjectBranchNameOrLatestRelease (..), ProjectBranchSpecifier (..), ProjectName, Semver)
 import Unison.Syntax.HashQualified qualified as HQ (fromString)
 import Unison.Syntax.Name qualified as Name (fromText, unsafeFromString)
 import Unison.Util.ColorText qualified as CT
@@ -1234,10 +1234,10 @@ pullImpl name aliases verbosity pullMode addendum = do
             maybeToEither (I.help self) . \case
               [] -> Just $ Input.PullRemoteBranchI Input.PullSourceTarget0 SyncMode.ShortCircuit pullMode verbosity
               [sourceString] -> do
-                source <- eitherToMaybe (parseReadRemoteNamespace "remote-namespace" sourceString)
+                source <- parsePullSource (Text.pack sourceString)
                 Just $ Input.PullRemoteBranchI (Input.PullSourceTarget1 source) SyncMode.ShortCircuit pullMode verbosity
               [sourceString, targetString] -> do
-                source <- eitherToMaybe (parseReadRemoteNamespace "remote-namespace" sourceString)
+                source <- parsePullSource (Text.pack sourceString)
                 target <- parseLooseCodeOrProject targetString
                 Just $
                   Input.PullRemoteBranchI
@@ -1275,7 +1275,7 @@ pullExhaustive =
               Input.PullWithHistory
               Verbosity.Verbose
         [sourceString] -> do
-          source <- eitherToMaybe (parseReadRemoteNamespace "remote-namespace" sourceString)
+          source <- parsePullSource (Text.pack sourceString)
           Just $
             Input.PullRemoteBranchI
               (Input.PullSourceTarget1 source)
@@ -1283,7 +1283,7 @@ pullExhaustive =
               Input.PullWithHistory
               Verbosity.Verbose
         [sourceString, targetString] -> do
-          source <- eitherToMaybe (parseReadRemoteNamespace "remote-namespace" sourceString)
+          source <- parsePullSource (Text.pack sourceString)
           target <- parseLooseCodeOrProject targetString
           Just $
             Input.PullRemoteBranchI
@@ -3253,6 +3253,10 @@ projectNameArg =
           isFinished = False
         }
 
+parsePullSource :: Text -> Maybe (ReadRemoteNamespace (These ProjectName ProjectBranchNameOrLatestRelease))
+parsePullSource =
+  P.parseMaybe (readRemoteNamespaceParser ProjectBranchSpecifier'NameOrLatestRelease)
+
 -- | Parse a 'Input.PushSource'.
 parsePushSource :: String -> Either (P.Pretty CT.ColorText) Input.PushSource
 parsePushSource sourceStr =

unison-cli/src/Unison/CommandLine/OutputMessages.hs

@@ -2163,6 +2163,8 @@ notifyUser dir = \case
         <> P.newline
         <> P.newline
         <> P.wrap "🎉 🥳 Happy coding!"
+  ProjectHasNoReleases projectName ->
+    pure . P.wrap $ prettyProjectName projectName <> "has no releases."
   where
     _nameChange _cmd _pastTenseCmd _oldName _newName _r = error "todo"
 
@@ -2781,7 +2783,7 @@ renderEditConflicts ppe Patch {..} = do
                  then "deprecated and also replaced with"
                  else "replaced with"
              )
-          `P.hang` P.lines replacements
+            `P.hang` P.lines replacements
     formatTermEdits ::
       (Reference.TermReference, Set TermEdit.TermEdit) ->
       Numbered Pretty
@@ -2796,7 +2798,7 @@ renderEditConflicts ppe Patch {..} = do
                  then "deprecated and also replaced with"
                  else "replaced with"
              )
-          `P.hang` P.lines replacements
+            `P.hang` P.lines replacements
     formatConflict ::
       Either
         (Reference, Set TypeEdit.TypeEdit)

unison-cli/tests/Unison/Test/UriParser.hs

@@ -12,13 +12,14 @@ import Unison.Codebase.Path qualified as Path
 import Unison.Codebase.ShortCausalHash (ShortCausalHash (..))
 import Unison.Core.Project (ProjectBranchName (..), ProjectName (..))
 import Unison.NameSegment (NameSegment (..))
+import Unison.Project (ProjectBranchSpecifier (..))
 
 test :: Test ()
 test =
   scope "uriparser" . tests $
     [ parserTests
         "repoPath"
-        (UriParser.repoPath <* P.eof)
+        (UriParser.readRemoteNamespaceParser ProjectBranchSpecifier'Name <* P.eof)
         [ ("unisonweb.base._releases.M4", looseR "unisonweb" ["base", "_releases", "M4"]),
           ("project", branchR (This "project")),
           ("/branch", branchR (That "branch")),

unison-cli/unison-cli.cabal

@@ -136,6 +136,7 @@ library
       GeneralizedNewtypeDeriving
       ImportQualifiedPost
       InstanceSigs
+      KindSignatures
       LambdaCase
       MultiParamTypeClasses
       MultiWayIf
@@ -208,6 +209,7 @@ library
     , text-builder
     , text-rope
     , these
+    , these-lens
     , time
     , transformers
     , unison-codebase
@@ -266,6 +268,7 @@ executable cli-integration-tests
       GeneralizedNewtypeDeriving
       ImportQualifiedPost
       InstanceSigs
+      KindSignatures
       LambdaCase
       MultiParamTypeClasses
       MultiWayIf
@@ -343,6 +346,7 @@ executable cli-integration-tests
     , text-builder
     , text-rope
     , these
+    , these-lens
     , time
     , transformers
     , unison-codebase
@@ -396,6 +400,7 @@ executable transcripts
       GeneralizedNewtypeDeriving
       ImportQualifiedPost
       InstanceSigs
+      KindSignatures
       LambdaCase
       MultiParamTypeClasses
       MultiWayIf
@@ -472,6 +477,7 @@ executable transcripts
     , text-builder
     , text-rope
     , these
+    , these-lens
     , time
     , transformers
     , unison-cli
@@ -531,6 +537,7 @@ executable unison
       GeneralizedNewtypeDeriving
       ImportQualifiedPost
       InstanceSigs
+      KindSignatures
       LambdaCase
       MultiParamTypeClasses
       MultiWayIf
@@ -608,6 +615,7 @@ executable unison
     , text-builder
     , text-rope
     , these
+    , these-lens
     , time
     , transformers
     , unison-cli
@@ -670,6 +678,7 @@ test-suite cli-tests
       GeneralizedNewtypeDeriving
       ImportQualifiedPost
       InstanceSigs
+      KindSignatures
       LambdaCase
       MultiParamTypeClasses
       MultiWayIf
@@ -747,6 +756,7 @@ test-suite cli-tests
     , text-builder
     , text-rope
     , these
+    , these-lens
     , time
     , transformers
     , unison-cli

unison-core/package.yaml

@@ -65,8 +65,10 @@ default-extensions:
   - DoAndIfThenElse
   - FlexibleContexts
   - FlexibleInstances
+  - GADTs
   - GeneralizedNewtypeDeriving
   - ImportQualifiedPost
+  - KindSignatures
   - LambdaCase
   - MultiParamTypeClasses
   - NamedFieldPuns

unison-core/src/Unison/Project.hs

@@ -12,6 +12,8 @@ module Unison.Project
     projectBranchNameUserSlug,
     ProjectBranchNameKind (..),
     classifyProjectBranchName,
+    ProjectBranchNameOrLatestRelease (..),
+    ProjectBranchSpecifier (..),
     ProjectAndBranch (..),
     projectAndBranchNamesParser,
     ProjectAndBranchNames (..),
@@ -23,6 +25,7 @@ module Unison.Project
 where
 
 import Data.Char qualified as Char
+import Data.Kind (Type)
 import Data.Text qualified as Text
 import Data.Text.Read qualified as Text (decimal)
 import Data.These (These (..))
@@ -271,6 +274,19 @@ projectBranchNameUserSlug (UnsafeProjectBranchName branchName) =
     then Just (Text.takeWhile (/= '/') (Text.drop 1 branchName))
     else Nothing
 
+-- | A project branch name, or the latest release of its project.
+data ProjectBranchNameOrLatestRelease
+  = ProjectBranchNameOrLatestRelease'LatestRelease
+  | ProjectBranchNameOrLatestRelease'Name !ProjectBranchName
+  deriving stock (Eq, Show)
+
+-- | How a project branch can be specified.
+data ProjectBranchSpecifier :: Type -> Type where
+  -- | By name.
+  ProjectBranchSpecifier'Name :: ProjectBranchSpecifier ProjectBranchName
+  -- | By name, or "the latest release"
+  ProjectBranchSpecifier'NameOrLatestRelease :: ProjectBranchSpecifier ProjectBranchNameOrLatestRelease
+
 instance From (ProjectAndBranch ProjectName ProjectBranchName) Text where
   from (ProjectAndBranch project branch) =
     Text.Builder.run $
@@ -343,7 +359,7 @@ instance From (These ProjectName ProjectBranchName) Text where
 
 instance TryFrom Text (These ProjectName ProjectBranchName) where
   tryFrom =
-    maybeTryFrom (Megaparsec.parseMaybe projectAndBranchNamesParser)
+    maybeTryFrom (Megaparsec.parseMaybe (projectAndBranchNamesParser ProjectBranchSpecifier'Name))
 
 -- Valid things:
 --
@@ -351,20 +367,33 @@ instance TryFrom Text (These ProjectName ProjectBranchName) where
 --   2. project/
 --   3. project/branch
 --   4. /branch
-projectAndBranchNamesParser :: Megaparsec.Parsec Void Text (These ProjectName ProjectBranchName)
-projectAndBranchNamesParser = do
+projectAndBranchNamesParser ::
+  forall branch.
+  ProjectBranchSpecifier branch ->
+  Megaparsec.Parsec Void Text (These ProjectName branch)
+projectAndBranchNamesParser specifier = do
   optional projectNameParser >>= \case
     Nothing -> do
       _ <- Megaparsec.char '/'
-      branch <- projectBranchNameParser False
+      branch <- branchParser
       pure (That branch)
     Just (project, hasTrailingSlash) ->
       if hasTrailingSlash
         then do
-          optional (projectBranchNameParser False) <&> \case
+          optional branchParser <&> \case
             Nothing -> This project
             Just branch -> These project branch
         else pure (This project)
+  where
+    branchParser :: Megaparsec.Parsec Void Text branch
+    branchParser =
+      case specifier of
+        ProjectBranchSpecifier'Name -> projectBranchNameParser False
+        ProjectBranchSpecifier'NameOrLatestRelease ->
+          asum
+            [ ProjectBranchNameOrLatestRelease'LatestRelease <$ "releases/latest",
+              ProjectBranchNameOrLatestRelease'Name <$> projectBranchNameParser False
+            ]
 
 -- | @project/branch@ syntax, where the branch is optional.
 instance From (ProjectAndBranch ProjectName (Maybe ProjectBranchName)) Text where

unison-core/unison-core1.cabal

@@ -71,8 +71,10 @@ library
       DoAndIfThenElse
       FlexibleContexts
       FlexibleInstances
+      GADTs
       GeneralizedNewtypeDeriving
       ImportQualifiedPost
+      KindSignatures
       LambdaCase
       MultiParamTypeClasses
       NamedFieldPuns
@@ -132,8 +134,10 @@ test-suite tests
       DoAndIfThenElse
       FlexibleContexts
       FlexibleInstances
+      GADTs
       GeneralizedNewtypeDeriving
       ImportQualifiedPost
+      KindSignatures
       LambdaCase
       MultiParamTypeClasses
       NamedFieldPuns