buildman: Allow specifying a range of commits to build

Adjust the -b flag to permit a range expression as well as a branch.

Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Tested-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/tools/buildman/README b/tools/buildman/README
index 8e7a68c..68456ce 100644
--- a/tools/buildman/README
+++ b/tools/buildman/README
@@ -699,6 +699,17 @@
 enabled automatically). Use -e to see errors/warnings as well.
 
 
+Building Ranges
+===============
+
+You can build a range of commits by specifying a range instead of a branch
+when using the -b flag. For example:
+
+    upstream/master..us-buildman
+
+will build commits in us-buildman that are not in upstream/master.
+
+
 Other options
 =============
 
diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index 2249b0f..e10ed86 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -123,14 +123,22 @@
     # problems introduced by the first commit on the branch.
     col = terminal.Color()
     count = options.count
+    has_range = options.branch and '..' in options.branch
     if count == -1:
         if not options.branch:
             count = 1
         else:
-            count, msg = gitutil.CountCommitsInBranch(options.git_dir,
-                                                      options.branch)
+            if has_range:
+                count, msg = gitutil.CountCommitsInRange(options.git_dir,
+                                                         options.branch)
+            else:
+                count, msg = gitutil.CountCommitsInBranch(options.git_dir,
+                                                          options.branch)
             if count is None:
                 sys.exit(col.Color(col.RED, msg))
+            elif count == 0:
+                sys.exit(col.Color(col.RED, "Range '%s' has no commits" %
+                                   options.branch))
             if msg:
                 print col.Color(col.YELLOW, msg)
             count += 1   # Build upstream commit also
@@ -172,8 +180,11 @@
     # to overwrite earlier ones by setting allow_overwrite=True
     if options.branch:
         if count == -1:
-            range_expr = gitutil.GetRangeInBranch(options.git_dir,
-                                                  options.branch)
+            if has_range:
+                range_expr = options.branch
+            else:
+                range_expr = gitutil.GetRangeInBranch(options.git_dir,
+                                                      options.branch)
             upstream_commit = gitutil.GetUpstream(options.git_dir,
                                                   options.branch)
             series = patchstream.GetMetaDataForList(upstream_commit,