Implement "b4 shazam -M" that execs git-merge

In addition to just being able to fetch a series into FETCH_HEAD, also
add an option to exec git-merge automatically so that people don't have
to cut-and-paste the merge command to use with paths to the cover
letter.

Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>

2 files changed, 59 insertions, 39 deletions

diff --git a/b4/command.py b/b4/command.py
index aa307da..4f69231 100644
--- a/b4/command.py
+++ b/b4/command.py
@@ -152,15 +152,18 @@ def cmd():
     sp_sh = subparsers.add_parser('shazam', help='Like b4 am, but applies the series to your tree')
     cmd_retrieval_common_opts(sp_sh)
     cmd_am_common_opts(sp_sh)
-    sp_sh.add_argument('-H', '--make-fetch-head', dest='makefetchhead', action='store_true', default=False,
-                       help='Attempt to treat series as a pull request and fetch it into FETCH_HEAD')
+    sh_g = sp_sh.add_mutually_exclusive_group()
+    sh_g.add_argument('-H', '--make-fetch-head', dest='makefetchhead', action='store_true', default=False,
+                      help='Attempt to treat series as a pull request and fetch it into FETCH_HEAD')
+    sh_g.add_argument('-M', '--merge', dest='merge', action='store_true', default=False,
+                      help='Attempt to merge series as if it were a pull request (execs git-merge)')
     sp_sh.add_argument('--guess-lookback', dest='guessdays', type=int, default=21,
-                       help=('(use with -H) When guessing base, go back this many days from the patch date '
+                       help=('(use with -H or -M) When guessing base, go back this many days from the patch date '
                              '(default: 3 weeks)'))
     sp_sh.set_defaults(func=cmd_shazam)
 
     # b4 attest
-    sp_att = subparsers.add_parser('attest', help='Create cryptographic attestation for a set of patches')
+    sp_att = subparsers.add_parser('attest', help='(DEPRECATED) Create cryptographic attestation for a set of patches')
     sp_att.add_argument('-f', '--from', dest='sender', default=None,
                         help='OBSOLETE: this option does nothing and will be removed')
     sp_att.add_argument('-n', '--no-submit', dest='nosubmit', action='store_true', default=False,
diff --git a/b4/mbox.py b/b4/mbox.py
index 4ac2c29..277df89 100644
--- a/b4/mbox.py
+++ b/b4/mbox.py
@@ -34,9 +34,9 @@ logger = b4.logger
 DEFAULT_MERGE_TEMPLATE = """Merge ${patch_or_series} "${seriestitle}"
 
 ${authorname} <${authoremail}> says:
-====================
-${coverletter}
-====================
+
+${covermessage}
+
 Link: ${midurl}
 """
 
@@ -263,7 +263,7 @@ def make_am(msgs, cmdargs, msgid):
         b4.save_git_am_mbox(am_msgs, ifh)
         ambytes = ifh.getvalue().encode()
         if not cmdargs.makefetchhead:
-            amflags = config.get('git-am-flags', '')
+            amflags = config.get('shazam-am-flags', '')
             sp = shlex.shlex(amflags, posix=True)
             sp.whitespace_split = True
             amargs = list(sp)
@@ -332,44 +332,59 @@ def make_am(msgs, cmdargs, msgid):
                 logger.critical(out.strip())
                 sys.exit(ecode)
             mmf = os.path.join(fhf.rstrip(), 'b4-cover')
+            merge_template = DEFAULT_MERGE_TEMPLATE
+            if config.get('shazam-merge-template'):
+                # Try to load this template instead
+                try:
+                    merge_template = b4.read_template(config['shazam-merge-template'])
+                except FileNotFoundError:
+                    logger.critical('ERROR: shazam-merge-template says to use %s, but it does not exist',
+                                    config['shazam-merge-template'])
+                    sys.exit(2)
+
+            # Write out a sample merge message using the cover letter
+            if os.path.exists(mmf):
+                # Make sure any old cover letters don't confuse anyone
+                os.unlink(mmf)
+
             if lser.has_cover:
-                merge_template = DEFAULT_MERGE_TEMPLATE
-                if config.get('shazam-merge-template'):
-                    # Try to load this template instead
-                    try:
-                        merge_template = b4.read_template(config['shazam-merge-template'])
-                    except FileNotFoundError:
-                        logger.critical('ERROR: shazam-merge-template says to use %s, but it does not exist',
-                                        config['shazam-merge-template'])
-                        sys.exit(2)
-
-                # Write out a sample merge message using the cover letter
                 cmsg = lser.patches[0]
                 parts = b4.LoreMessage.get_body_parts(cmsg.body)
-                tptvals = {
-                        'seriestitle': cmsg.subject,
-                        'authorname': cmsg.fromname,
-                        'authoremail': cmsg.fromemail,
-                        'coverletter': parts[1],
-                        'midurl': linkurl,
-                        }
-                if len(am_msgs) > 1:
-                    tptvals['patch_or_series'] = 'patch series'
-                else:
-                    tptvals['patch_or_series'] = 'patch'
+                covermessage = parts[1]
+            else:
+                cmsg = lser.patches[1]
+                covermessage = ('NOTE: No cover letter provided by the author.\n'
+                                '      Add merge commit message here.')
+            tptvals = {
+                'seriestitle': cmsg.subject,
+                'authorname': cmsg.fromname,
+                'authoremail': cmsg.fromemail,
+                'covermessage': covermessage,
+                'midurl': linkurl,
+            }
+            if len(am_msgs) > 1:
+                tptvals['patch_or_series'] = 'patch series'
+            else:
+                tptvals['patch_or_series'] = 'patch'
 
-                body = Template(merge_template).safe_substitute(tptvals)
-                with open(mmf, 'w') as mmh:
-                    mmh.write(body)
+            body = Template(merge_template).safe_substitute(tptvals)
+            with open(mmf, 'w') as mmh:
+                mmh.write(body)
 
-            elif os.path.exists(mmf):
-                # Make sure any old cover letters don't confuse anyone
-                os.unlink(mmf)
+        mergeflags = config.get('shazam-merge-flags', '--signoff')
+        sp = shlex.shlex(mergeflags, posix=True)
+        sp.whitespace_split = True
+        mergeargs = ['merge', '--no-ff', '-F', mmf, '--edit', 'FETCH_HEAD'] + list(sp)
+        mergecmd = ['git'] + mergeargs
 
-        logger.info('You can now merge or checkout FETCH_HEAD')
-        if lser.has_cover:
-            logger.info('  e.g.: git merge -F $(git rev-parse --git-dir)/b4-cover --signoff --edit FETCH_HEAD')
         thanks_record_am(lser, cherrypick=cherrypick)
+        if cmdargs.merge:
+            # We exec git-merge and let it take over
+            logger.info('Invoking: %s', ' '.join(mergecmd))
+            os.execvp(mergecmd[0], mergecmd)
+
+        logger.info('You can now merge or checkout FETCH_HEAD')
+        logger.info('  e.g.: %s', ' '.join(mergecmd))
         return
 
     if not base_commit:
@@ -711,6 +726,8 @@ def main(cmdargs):
         cmdargs.nopartialreroll = False
         cmdargs.outdir = '-'
         cmdargs.guessbranch = None
+        if cmdargs.merge:
+            cmdargs.makefetchhead = True
         if cmdargs.makefetchhead:
             cmdargs.guessbase = True
         else: