[RFC] MAINTAINERS tag for cleanup robot

[Joe Perches]

On Sun, 2020-11-22 at 08:33 -0800, Tom Rix wrote:
> On 11/21/20 9:10 AM, Joe Perches wrote:
> > On Sat, 2020-11-21 at 08:50 -0800, trix at redhat.com wrote:
> > > A difficult part of automating commits is composing the subsystem
> > > preamble in the commit log.  For the ongoing effort of a fixer producing
> > > one or two fixes a release the use of 'treewide:' does not seem appropriate.
> > > 
> > > It would be better if the normal prefix was used.  Unfortunately normal is
> > > not consistent across the tree.
> > > 
> > > So I am looking for comments for adding a new tag to the MAINTAINERS file
> > > 
> > > 	D: Commit subsystem prefix
> > > 
> > > ex/ for FPGA DFL DRIVERS
> > > 
> > > 	D: fpga: dfl:
> > I'm all for it.  Good luck with the effort.  It's not completely trivial.
> > 
> > From a decade ago:
> > 
> > https://lore.kernel.org/lkml/1289919077.28741.50.camel@Joe-Laptop/
> > 
> > (and that thread started with extra semicolon patches too)
> 
> Reading the history, how about this.
> 
> get_maintainer.pl outputs a single prefix, if multiple files have the
> same prefix it works, if they don't its an error.
> 
> Another script 'commit_one_file.sh' does the call to get_mainainter.pl
> to get the prefix and be called by run-clang-tools.py to get the fixer
> specific message.

It's not whether the script used is get_maintainer or any other script,
the question is really if the MAINTAINERS file is the appropriate place
to store per-subsystem patch specific prefixes.

It is.

Then the question should be how are the forms described and what is the
inheritance priority.  My preference would be to have a default of
inherit the parent base and add basename(subsystem dirname).

Commit history seems to have standardized on using colons as the separator
between the commit prefix and the subject.

A good mechanism to explore how various subsystems have uses prefixes in
the past might be something like:

$ git log --no-merges --pretty='%s' -<commit_count> <subsystem_path> | \
  perl -n -e 'print substr($_, 0, rindex($_, ":") + 1) . "\n";' | \
  sort | uniq -c | sort -rn

Using 10000 for commit_count and drivers/scsi for subsystem_path, the
top 40 entries are below:

About 1% don't have a colon, and there is no real consistency even
within individual drivers below scsi.  For instance, qla2xxx:

     1	    814 scsi: qla2xxx:
     2	    691 scsi: lpfc:
     3	    389 scsi: hisi_sas:
     4	    354 scsi: ufs:
     5	    339 scsi:
     6	    291 qla2xxx:
     7	    256 scsi: megaraid_sas:
     8	    249 scsi: mpt3sas:
     9	    200 hpsa:
    10	    190 scsi: aacraid:
    11	    174 lpfc:
    12	    153 scsi: qedf:
    13	    144 scsi: smartpqi:
    14	    139 scsi: cxlflash:
    15	    122 scsi: core:
    16	    110 [SCSI] qla2xxx:
    17	    108 ncr5380:
    18	     98 scsi: hpsa:
    19	     97 
    20	     89 treewide:
    21	     88 mpt3sas:
    22	     86 scsi: libfc:
    23	     85 scsi: qedi:
    24	     84 scsi: be2iscsi:
    25	     81 [SCSI] qla4xxx:
    26	     81 hisi_sas:
    27	     81 block:
    28	     75 megaraid_sas:
    29	     71 scsi: sd:
    30	     69 [SCSI] hpsa:
    31	     68 cxlflash:
    32	     65 scsi: libsas:
    33	     65 scsi: fnic:
    34	     61 scsi: scsi_debug:
    35	     60 scsi: arcmsr:
    36	     57 be2iscsi:
    37	     53 atp870u:
    38	     51 scsi: bfa:
    39	     50 scsi: storvsc:
    40	     48 sd: