[PATCH b4 1/2] diff: add a creation factor argument

[Antonin Godard <antonin.godard@bootlin.com>]

When using git range-diff it is possible to override the creation factor
when git considers a large change a total rewrite (and so showing no
diff at all), or a change so small it shouldn't be considered.

This parameter is only possible to set from command-line, it has no
global option associated to it within Git's config, so add a
--creation-factor parameter to b4 to achieve the same behavior.

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
---
 src/b4/command.py | 2 ++
 src/b4/diff.py    | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/b4/command.py b/src/b4/command.py
index 2bdd785..0485196 100644
--- a/src/b4/command.py
+++ b/src/b4/command.py
@@ -287,6 +287,8 @@ def setup_parser() -> argparse.ArgumentParser:
                          help='Force color output even when writing to file')
     sp_diff.add_argument('-m', '--compare-am-mboxes', dest='ambox', nargs=2, default=None,
                          help='Compare two mbx files prepared with "b4 am"')
+    sp_diff.add_argument('--creation-factor', default=None, type=int,
+                         help='Creation factor integer passed to git range-diff')
     sp_diff.set_defaults(func=cmd_diff)
 
     # b4 kr
diff --git a/src/b4/diff.py b/src/b4/diff.py
index 1de3063..83fad67 100644
--- a/src/b4/diff.py
+++ b/src/b4/diff.py
@@ -156,7 +156,10 @@ def main(cmdargs: argparse.Namespace) -> None:
         logger.critical('---')
         logger.critical('Could not create fake-am range for upper series v%s', user.revision)
         sys.exit(1)
-    grdcmd = 'git range-diff %.12s..%.12s %.12s..%.12s' % (lsc, lec, usc, uec)
+    cf_str = ""
+    if cmdargs.creation_factor:
+        cf_str = f"--creation-factor={cmdargs.creation_factor} "
+    grdcmd = 'git range-diff %s%.12s..%.12s %.12s..%.12s' % (cf_str, lsc, lec, usc, uec)
     if cmdargs.nodiff:
         logger.info('Success, to compare v%s and v%s:', lser.revision, user.revision)
         logger.info(f'    {grdcmd}')
@@ -167,6 +170,8 @@ def main(cmdargs: argparse.Namespace) -> None:
     gitargs = ['range-diff', f'{lsc}..{lec}', f'{usc}..{uec}']
     if cmdargs.outdiff is None or cmdargs.color:
         gitargs.append('--color')
+    if cmdargs.creation_factor:
+        gitargs.append(cf_str.strip())
     ecode, rdiff = b4.git_run_command(cmdargs.gitdir, gitargs)
     if ecode > 0:
         logger.critical('Unable to generate diff')

-- 
2.47.0