improve getCommitHashes

`getCommitHashes` now returns at least one commit, and reverses commits
by default (ie. oldest to newset).

2 files changed, 8 insertions, 10 deletions

diff --git a/app/Git.hs b/app/Git.hs
index af02b70..653ddbd 100644
--- a/app/Git.hs
+++ b/app/Git.hs
@@ -5,11 +5,14 @@ module Git
   )
 where
 
-import Control.Exception (finally)
+import Control.Exception (finally, throw)
 import Data.ByteString.Lazy.Char8 qualified as LB8
+import Data.List.NonEmpty (NonEmpty)
+import Data.List.NonEmpty qualified as N
 import Data.Maybe (fromMaybe)
 import Data.Text qualified as T
 import Data.Text.Encoding qualified as T
+import Exception qualified as E
 import Process (proc, sh, sh_)
 import System.Directory (createDirectoryIfMissing)
 import System.FilePath (dropTrailingPathSeparator, takeDirectory)
@@ -22,8 +25,8 @@ withWorkingTree path hash action = do
   action `finally` do
     sh_ $ proc "git worktree remove --force %" path
 
-getCommitHashes :: IO [T.Text]
-getCommitHashes = T.lines . T.decodeUtf8 . LB8.toStrict <$> sh "git log --format=%H"
+getCommitHashes :: IO (NonEmpty T.Text)
+getCommitHashes = fromMaybe (throw E.NoCommits) . N.nonEmpty . reverse . T.lines . T.decodeUtf8 . LB8.toStrict <$> sh "git log --format=%H"
 
 getRootDir :: IO FilePath
 getRootDir = T.unpack . stripTrailingNL . T.decodeUtf8 . LB8.toStrict <$> sh (proc "git rev-parse --show-toplevel")
diff --git a/app/History/PartialCommitInfo.hs b/app/History/PartialCommitInfo.hs
index 2337ef7..cd8cd46 100644
--- a/app/History/PartialCommitInfo.hs
+++ b/app/History/PartialCommitInfo.hs
@@ -8,6 +8,7 @@ import Control.Exception (catch)
 import Data.Binary (Binary)
 import Data.ByteString.Lazy.Char8 qualified as LB8
 import Data.Function ((&))
+import Data.List.NonEmpty qualified as N
 import Data.Text qualified as T
 import Die (die)
 import Exception qualified as E
@@ -35,13 +36,7 @@ data PartialCommitInfo = PartialCommitInfo
 
 getPartialCommitInfos :: IO [PartialCommitInfo]
 getPartialCommitInfos = do
-  -- TODO Revise `getCommitHashes`
-  --
-  -- - Should throw if no commits.
-  -- - Should always be reversed?
-  --
-  -- @difficulty easy
-  commitHashes <- reverse <$> Git.getCommitHashes
+  commitHashes <- N.toList <$> Git.getCommitHashes
   parMapM getCommitInfoOf (map Commit commitHashes ++ [WorkingTree])
 
 getCommitInfoOf :: CommitHash -> IO PartialCommitInfo