fix: allow for using busybox grep

ugh

apatch

@@ -44,7 +44,8 @@ abuild clean fetch unpack default_prepare
 startdir="$PWD"
 srcdir="$startdir/src"
 . APKBUILD
-test -n "$builddir" || builddir="$srcdir/$pkgname-$pkgver"
+unset -f grep cut head git rm mv
+[ -n "$builddir" ] || builddir="$srcdir/$pkgname-$pkgver"
 
 patchpath="$startdir/$1"
 
@@ -67,7 +68,8 @@ if [ -f "$patchpath" ]; then
   msg "patch exists, trying to extract existing message"
   # try to extract the original header from the patch
   patch_start=$(grep -En '^(diff --git|--- )' "$patchpath" | cut -d: -f1 | head -n 1)
-  header="$(head -n $(( patch_start - 1 )) "$patchpath"; echo)"
+  header_file="/tmp/$(mktemp -u apatch.XXXXXX)"
+  head -n $(( patch_start - 1 )) "$patchpath" > "$header_file"
 fi
 
 (
@@ -79,7 +81,7 @@ fi
   # if file exists, try to apply
   if [ -e "$patchpath" ]; then
     git apply --reject --whitespace=fix "$patchpath" || {
-      rejects="$(git status --porcelain | grep '\?\? .*\.rej$' | cut -c4-)"
+      rejects="$(git status --porcelain | grep -F '??' | grep -F '.rej' | cut -c4-)"
       if [ -n "$rejects" ]; then
         warning "$1 partially applied with rejects"
         for reject in $rejects; do
@@ -92,7 +94,7 @@ fi
           rm "$target.porig" # left by wiggle
         done
       else
-        warning "$patch failed to apply"
+        warning "$1 failed to apply"
       fi
     }
   fi
@@ -103,7 +105,10 @@ fi
   git add .
 
   msg "saving patch $1"
-  echo -n "$header" > "$patchpath"
+  echo -n > "$patchpath" # empty the file first
+  if [ -n "$header_file" ]; then
+     mv "$header_file" "$patchpath"
+  fi
   git diff --cached >> "$patchpath"
 
   if [ ! -s "$patchpath" ]; then