patman: Allow skipping patches at the end

The -s option allows skipping patches at the top of the branch. Sometimes
there are commits at the bottom that need to be skipped. At present it is
necessary to count the number of commits and then use -c to tell patman
how many to process.

Add a -e option to easily skip a number of commits at the bottom of the
branch.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/control.py b/tools/patman/control.py
index b48eac4..b481ff6 100644
--- a/tools/patman/control.py
+++ b/tools/patman/control.py
@@ -20,7 +20,7 @@
     """Do required setup before doing anything"""
     gitutil.Setup()
 
-def prepare_patches(col, branch, count, start, ignore_binary):
+def prepare_patches(col, branch, count, start, end, ignore_binary):
     """Figure out what patches to generate, then generate them
 
     The patch files are written to the current directory, e.g. 0001_xxx.patch
@@ -32,6 +32,8 @@
         count (int): Number of patches to produce, or -1 to produce patches for
             the current branch back to the upstream commit
         start (int): Start partch to use (0=first / top of branch)
+        end (int): End patch to use (0=last one in series, 1=one before that,
+            etc.)
         ignore_binary (bool): Don't generate patches for binary files
 
     Returns:
@@ -50,7 +52,7 @@
                            'No commits found to process - please use -c flag'))
 
     # Read the metadata from the commits
-    to_do = count
+    to_do = count - end
     series = patchstream.GetMetaData(branch, start, to_do)
     cover_fname, patch_files = gitutil.CreatePatches(
         branch, start, to_do, ignore_binary, series)
@@ -159,7 +161,7 @@
     setup()
     col = terminal.Color()
     series, cover_fname, patch_files = prepare_patches(
-        col, options.branch, options.count, options.start,
+        col, options.branch, options.count, options.start, options.end,
         options.ignore_binary)
     ok = check_patches(series, patch_files, options.check_patch,
                        options.verbose)
diff --git a/tools/patman/func_test.py b/tools/patman/func_test.py
index 588be73e..810af9c 100644
--- a/tools/patman/func_test.py
+++ b/tools/patman/func_test.py
@@ -430,7 +430,8 @@
             col = terminal.Color()
             with capture_sys_output() as _:
                 _, cover_fname, patch_files = control.prepare_patches(
-                    col, branch=None, count=-1, start=0, ignore_binary=False)
+                    col, branch=None, count=-1, start=0, end=0,
+                    ignore_binary=False)
             self.assertIsNone(cover_fname)
             self.assertEqual(2, len(patch_files))
 
@@ -438,9 +439,17 @@
             self.assertEqual(3, gitutil.CountCommitsToBranch('second'))
             with capture_sys_output() as _:
                 _, cover_fname, patch_files = control.prepare_patches(
-                    col, branch='second', count=-1, start=0,
+                    col, branch='second', count=-1, start=0, end=0,
                     ignore_binary=False)
             self.assertIsNotNone(cover_fname)
             self.assertEqual(3, len(patch_files))
+
+            # Check that it can skip patches at the end
+            with capture_sys_output() as _:
+                _, cover_fname, patch_files = control.prepare_patches(
+                    col, branch='second', count=-1, start=0, end=1,
+                    ignore_binary=False)
+            self.assertIsNotNone(cover_fname)
+            self.assertEqual(2, len(patch_files))
         finally:
             os.chdir(orig_dir)
diff --git a/tools/patman/main.py b/tools/patman/main.py
index 0667541..4d7a304 100755
--- a/tools/patman/main.py
+++ b/tools/patman/main.py
@@ -35,6 +35,8 @@
                   help="Branch to process (by default, the current branch)")
 parser.add_option('-c', '--count', dest='count', type='int',
        default=-1, help='Automatically create patches from top n commits')
+parser.add_option('-e', '--end', type='int', default=0,
+                  help='Commits to skip at end of patch list')
 parser.add_option('-i', '--ignore-errors', action='store_true',
        dest='ignore_errors', default=False,
        help='Send patches email even if patch errors are found')