patch, 2 partsAdd a new flag, --spill, to stg delete

diff --git a/stgit/commands/delete.py b/stgit/commands/delete.py
index 1b59cdd..015fb49 100644
--- a/stgit/commands/delete.py
+++ b/stgit/commands/delete.py
@@ -30,6 +30,13 @@ Delete the patches passed as arguments."""
 args = [argparse.patch_range(argparse.applied_patches,
                              argparse.unapplied_patches)]
 options = [
+    opt('--spill', action = 'store_true',
+        short = 'Spill patch contents to worktree and index', long = """
+        Delete the patches, but do not touch the index and worktree.
+        This only works with applied patches at the top of the stack.
+        The effect is to "spill" the patch contents into the index and
+        worktree. This can be useful e.g. if you want to split a patch
+        into several smaller pieces."""),
     opt('-b', '--branch', args = [argparse.stg_branches],
         short = 'Use BRANCH instead of the default branch')]
 
@@ -46,6 +53,12 @@ def func(parser, options, args):
         patches = set(common.parse_patches(args, list(stack.patchorder.all)))
     else:
         parser.error('No patches specified')
+
+    if options.spill:
+        if set(stack.patchorder.applied[-len(patches):]) != patches:
+            parser.error('Can only spill topmost applied patches')
+        iw = None # don't touch index+worktree
+
     def allow_conflicts(trans):
         # Allow conflicts if the topmost patch stays the same.
         if stack.patchorder.applied:

diff --git a/t/t1602-delete-spill.sh b/t/t1602-delete-spill.sh
new file mode 100755
index 0000000..1ddec53
--- /dev/null
+++ b/t/t1602-delete-spill.sh
@@ -0,0 +1,47 @@
+#!/bin/sh
+test_description='Test "stg delete --spill"'
+. ./test-lib.sh
+
+test_expect_success 'Initialize the StGIT repository' '
+    stg init
+'
+
+test_expect_success 'Create five applied and three unapplied patches' '
+    for i in 0 1 2 3 4 5 6 7; do
+        echo $i >> foo &&
+        git add foo &&
+        git commit -m p$i
+    done
+    stg uncommit -n 8 &&
+    stg pop -n 3
+'
+
+test_expect_success 'Try to delete --spill an unapplied patch' '
+    command_error stg delete --spill p7 &&
+    test "$(echo $(stg series))" = "+ p0 + p1 + p2 + p3 > p4 - p5 - p6 - p7" &&
+    test "$(echo $(cat foo))" = "0 1 2 3 4" &&
+    test "$(echo $(git diff-files))" = ""
+'
+
+test_expect_success 'Try to delete --spill a non-top patch' '
+    command_error stg delete --spill p2 &&
+    test "$(echo $(stg series))" = "+ p0 + p1 + p2 + p3 > p4 - p5 - p6 - p7" &&
+    test "$(echo $(cat foo))" = "0 1 2 3 4" &&
+    test "$(echo $(git diff-files))" = ""
+'
+
+test_expect_success 'Delete --spill one patch' '
+    stg delete --spill p4 &&
+    test "$(echo $(stg series))" = "+ p0 + p1 + p2 > p3 - p5 - p6 - p7" &&
+    test "$(echo $(cat foo))" = "0 1 2 3 4" &&
+    test "$(echo $(git diff-files))" = ""
+'
+
+test_expect_success 'Delete --spill several patches' '
+    stg delete --spill p2 p3 p1 &&
+    test "$(echo $(stg series))" = "> p0 - p5 - p6 - p7" &&
+    test "$(echo $(cat foo))" = "0 1 2 3 4" &&
+    test "$(echo $(git diff-files))" = ""
+'
+
+test_done