improve getCommitHashes

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

1 files changed, 6 insertions, 3 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")