[repro] Rework PKGBUILD fetching

Some PKGBUILDs use _pkgver and so on, so we are unable to count on them being
"correct" when fetching PKGBUILDs. We also never implemented support for epoch.
Another problem is that we can't go over the commit history and look at `updpkg:
...` values as they might not be there.

Instead we traverse the history and find the correct PKGBUILD by checksumming it
against the one in the PKGBUILD.

Signed-off-by: Morten Linderud <morten@linderud.pw>

Author: Foxboron

repro.in

@@ -241,18 +241,17 @@ install -d -o builduser -g builduser /startdir
 pacman -S asp --noconfirm
 asp checkout $pkgbase
 cd $pkgbase
-history=\$(git grep --all-match -e pkgver=$pkgver -e pkgrel=$pkgrel \$(git rev-list --all -- repos/) -- repos/)
-cut -d: -f1 <<< \$history | head -1 | xargs git checkout
-file_path=\$(cut -d: -f2 <<< \$history | head -1 | xargs dirname)
-pkgbuild_checksum=\$(sha256sum -b \$file_path/PKGBUILD)
-pkgbuild_checksum=\${pkgbuild_checksum%% *}
-if [ \$pkgbuild_checksum != $pkgbuild_sha256sum ]; then
-    # TODO: use warning or exit
-    echo "Warning PKGBUILD checksum does not match"
-	exit 1
-fi
-mv ./\$file_path/* /startdir
-pacman -Rs asp --noconfirm
+for rev in \$(git rev-list --all -- repos/); do
+    pkgbuild_checksum=\$(git show \$rev:trunk/PKGBUILD | sha256sum -b)
+    pkgbuild_checksum=\${pkgbuild_checksum%% *}
+    if [ \$pkgbuild_checksum = $pkgbuild_sha256sum ]; then
+        git checkout \$rev
+        mv ./trunk/* /startdir
+        pacman -Rs asp --noconfirm
+        exit 0
+    fi
+done
+exit 1
 __END__
 
     msg2 "Preparing packages"