From a8d20ee46e04acf0cd08405d6234ce6a0eca22aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6gler?= <ck3d@gmx.de>
Date: Sun, 7 Feb 2021 19:41:01 +0100
Subject: [PATCH] GitInput: Avoid fetch if rev is available

Similar to libfetcher in Nix, avoid fetching if rev is already
available.
---
 src/lib/Hydra/Plugin/GitInput.pm | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/lib/Hydra/Plugin/GitInput.pm b/src/lib/Hydra/Plugin/GitInput.pm
index 3fbf50f0..f2b3a653 100644
--- a/src/lib/Hydra/Plugin/GitInput.pm
+++ b/src/lib/Hydra/Plugin/GitInput.pm
@@ -141,14 +141,19 @@ sub fetchInput {
         die "error creating git repo in `$clonePath':\n$res->{stderr}" if $res->{status};
     }
 
-    # This command forces the update of the local branch to be in the same as
-    # the remote branch for whatever the repository state is.  This command mirrors
-    # only one branch of the remote repository.
-    my $localBranch = _isHash($branch) ? "_hydra_tmp" : $branch;
-    $res = run(cmd => ["git", "fetch", "-fu", "origin", "+$branch:$localBranch"], dir => $clonePath,
-               timeout => $cfg->{timeout});
-    $res = run(cmd => ["git", "fetch", "-fu", "origin"], dir => $clonePath, timeout => $cfg->{timeout}) if $res->{status};
-    die "error fetching latest change from git repo at `$uri':\n$res->{stderr}" if $res->{status};
+    $res = run(cmd => ["git", "cat-file", "-t", $branch], dir => $clonePath);
+    if (! _isHash($branch) || $res->{status}) {
+        # This command forces the update of the local branch to be in the same as
+        # the remote branch for whatever the repository state is.  This command mirrors
+        # only one branch of the remote repository.
+        my $localBranch = _isHash($branch) ? "_hydra_tmp" : $branch;
+        $res = run(cmd => ["git", "fetch", "-fu", "origin", "+$branch:$localBranch"], dir => $clonePath,
+                   timeout => $cfg->{timeout});
+        $res = run(cmd => ["git", "fetch", "-fu", "origin"], dir => $clonePath, timeout => $cfg->{timeout}) if $res->{status};
+        die "error fetching latest change from git repo at `$uri':\n$res->{stderr}" if $res->{status};
+    } else {
+        $res = run(cmd => ["git", "branch", "-f", "_hydra_tmp", "$branch"], dir => $clonePath, timeout => $cfg->{timeout});
+    }
 
     # If deepClone is defined, then we look at the content of the repository
     # to determine if this is a top-git branch.