[StGit PATCH] edit: Allow setting git tree SHA1 of a patch

["Gustav Hållberg" <gustav@gmail.com>]

I would like to have something similar to this patch, which allows for
setting the (git) tree of a particular patch. I would like to use it
(from the Emacs mode) to make it easier to split an old patch into two
(or more).

It might be that this is too "powerful" (read: unsafe), and maybe a
better (safer) command would use whatever is currently in the index
rather than a SHA1.

Anyway, I'd appreciate any comments, e.g. at
http://github.com/gustavh/stgit/commits/set-tree (pull from
git://github.com/gustavh/stgit.git "set-tree" branch).

---
Also fix capitalization in edit's short description.

Signed-off-by: Gustav Hållberg <gustav@gmail.com>
---
 stgit/commands/edit.py |   19 ++++++++++++++++---
 t/t3300-edit.sh        |   15 +++++++++++++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/stgit/commands/edit.py b/stgit/commands/edit.py
index f3f731f..55282f4 100644
--- a/stgit/commands/edit.py
+++ b/stgit/commands/edit.py
@@ -24,7 +24,7 @@ from stgit.commands import common
 from stgit.lib import git as gitlib, transaction, edit
 from stgit.out import *
 
-help = 'edit a patch description or diff'
+help = 'Edit a patch description or diff'
 kind = 'patch'
 usage = ['[options] [--] [<patch>]']
 description = """
@@ -52,7 +52,11 @@ invoked even if such command-line options are given.)
 
 If the patch diff is edited but does not apply, no changes are made to
 the patch at all. The edited patch is saved to a file which you can
-feed to "stg edit --file", once you have made sure it does apply."""
+feed to "stg edit --file", once you have made sure it does apply.
+
+With --set-tree you set the git tree of the patch to the specified
+SHA1, without changing the tree of any other patches. See also the
+--set-tree flag of stg push."""
 
 args = [argparse.applied_patches, argparse.unapplied_patches,
         argparse.hidden_patches]
@@ -61,6 +65,9 @@ options = [
         short = 'Edit the patch diff'),
     opt('-e', '--edit', action = 'store_true',
         short = 'Invoke interactive editor'),
+    opt('-t', '--set-tree', action = 'store',
+        metavar = 'SHA1',
+        short = 'Set the git tree of the patch to SHA1'),
     ] + (argparse.sign_options() +
          argparse.message_options(save_template = True) +
          argparse.author_options() + argparse.diff_opts_option())
@@ -86,6 +93,9 @@ def func(parser, options, args):
 
     cd = orig_cd = stack.patches.get(patchname).commit.data
 
+    if options.set_tree:
+        cd = cd.set_tree(stack.repository.get_tree(options.set_tree))
+
     cd, failed_diff = edit.auto_edit_patch(
         stack.repository, cd, msg = options.message, contains_diff = True,
         author = options.author, committer = lambda p: p,
@@ -128,7 +138,10 @@ def func(parser, options, args):
     trans.patches[patchname] = stack.repository.commit(cd)
     try:
         for pn in popped:
-            trans.push_patch(pn, iw, allow_interactive = True)
+            if options.set_tree:
+                trans.push_tree(pn)
+            else:
+                trans.push_patch(pn, iw, allow_interactive = True)
     except transaction.TransactionHalted:
         pass
     try:
diff --git a/t/t3300-edit.sh b/t/t3300-edit.sh
index 7003a27..078d4c3 100755
--- a/t/t3300-edit.sh
+++ b/t/t3300-edit.sh
@@ -212,4 +212,19 @@ test_expect_failure 'Fail to set invalid author date' '
     test "$(date HEAD)" = "2013-01-28 22:30:00 -0300"
 '
 
+test_expect_success 'Set patch tree SHA1' '
+    p2tree=$(git log -1 --pretty=format:%T $(stg id p2)) &&
+    p4tree=$(git log -1 --pretty=format:%T $(stg id p4)) &&
+    stg edit --set-tree $p4tree &&
+    test $(git write-tree) = $p4tree &&
+    grep "^333zz$" foo &&
+    stg pop &&
+    stg edit --set-tree $p2tree p2 &&
+    stg push --set-tree &&
+    test $(git write-tree) = $p2tree &&
+    grep "^333$" foo &&
+    stg edit --set-tree $p2tree p1 &&
+    test "$(echo $(stg series --empty --all))" = "+ p1 0> p2 - p3 ! p4"
+'
+
 test_done