about get_maintainer.pl not showing the original author of the modified code

about get_maintainer.pl not showing the original author of the modified code

[Jianyu Zhan]

Hi, Joe,

recently in this patch https://lkml.org/lkml/2016/3/2/281,

I found the original author of the modified code was not
suggested as a patch reviewer.

This surprised me at first.  But later I realized that it is not trivial
to define "original author", since the last modification might be
just code polishing.  To dig out the original author, we might need
go up the commit history and git must be equipped with ability of pattern
recognization to analyze code.

What do you think?

Regards,
Jianyu Zhan

Re: about get_maintainer.pl not showing the original author of the modified code

[Joe Perches]

On Thu, 2016-03-03 at 11:00 +0800, Jianyu Zhan wrote:
> Hi, Joe,
> 
> recently in this patch https://lkml.org/lkml/2016/3/2/281,
> 
> I found the original author of the modified code was not
> suggested as a patch reviewer.
> 
> This surprised me at first.  But later I realized that it is not trivial
> to define "original author", since the last modification might be
> just code polishing.  To dig out the original author, we might need
> go up the commit history and git must be equipped with ability of pattern
> recognization to analyze code.
> 
> What do you think?

There are many options to the get_maintainer script.
You can see all of them with "./scripts/get_maintainer.pl --help"

Many are not enabled because run-time can be very long as
running various git commands can take awhile to complete.

$ ./scripts/get_maintainer.pl --git-blame <patch|-f <file>>

with your patch get_maintainer.pl and --git-blame gives:

$ ./scripts/get_maintainer.pl ~/1.diff --git-blame
Thomas Gleixner <tglx@linutronix.de> (commit_signer:20/19=100%,authored:7/19=37%,added_lines:73/248=29%,removed_lines:38/119=32%)
Peter Zijlstra <peterz@infradead.org> (commit_signer:3/19=16%,authored:1/19=5%)
Andrew Morton <akpm@linux-foundation.org> (commit_signer:3/19=16%,modified commits:2/3=67%)
Davidlohr Bueso <dave@stgolabs.net> (commit_signer:3/19=16%,authored:3/19=16%,added_lines:113/248=46%,removed_lines:20/119=17%)
Ingo Molnar <mingo@kernel.org> (commit_signer:2/19=11%,modified commits:2/3=67%)
Dominik Dingel <dingel@linux.vnet.ibm.com> (authored:1/19=5%)
Jann Horn <jann@thejh.net> (authored:1/19=5%)
Sebastian Andrzej Siewior <bigeasy@linutronix.de> (added_lines:29/248=12%)
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> (added_lines:14/248=6%,removed_lines:49/119=41%)
Darren Hart <dvhart@linux.intel.com> (modified commits:1/3=33%)
Stephen Hemminger <shemminger@linux-foundation.org> (modified commits:1/3=33%)
Christian Borntraeger <borntrae@de.ibm.com> (modified commits:1/3=33%)
linux-kernel@vger.kernel.org (open list)

vs

$ ./scripts/get_maintainer.pl ~/1.diff
Thomas Gleixner <tglx@linutronix.de> (commit_signer:20/19=100%,authored:7/19=37%,added_lines:73/248=29%,removed_lines:38/119=32%)
Davidlohr Bueso <dave@stgolabs.net> (commit_signer:3/19=16%,authored:3/19=16%,added_lines:113/248=46%,removed_lines:20/119=17%)
Peter Zijlstra <peterz@infradead.org> (commit_signer:3/19=16%)
Andrew Morton <akpm@linux-foundation.org> (commit_signer:3/19=16%)
Ingo Molnar <mingo@kernel.org> (commit_signer:2/19=11%)
Rasmus Villemoes <linux@rasmusvillemoes.dk> (authored:1/19=5%)
Darren Hart <dvhart@linux.intel.com> (authored:1/19=5%)
kbuild test robot <fengguang.wu@intel.com> (authored:1/19=5%)
Sebastian Andrzej Siewior <bigeasy@linutronix.de> (added_lines:29/248=12%)
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> (added_lines:14/248=6%,removed_lines:49/119=41%)

running git blame alone gives:

$ git blame -L1927,+8 kernel/futex.c
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1927) 
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1928)         /* In the common case we don't take the spinlock, which is nice. */
42d35d48 (Darren Hart           2008-12-29 15:49:53 -0800 1929) retry:
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1930)         lock_ptr = q->lock_ptr;
e91467ec (Christian Borntraeger 2006-08-05 12:13:52 -0700 1931)         barrier();
c80544dc (Stephen Hemminger     2007-10-18 03:07:05 -0700 1932)         if (lock_ptr != NULL) {
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1933)                 spin_lock(lock_ptr);
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1934)                 /*

with whitespace ignored, it gives:

$ git blame -w -L1927,+8 kernel/futex.c 
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1927) 
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1928)         /* In the common case we don't take the spinlock, which is nice. */
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1929) retry:
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1930)         lock_ptr = q->lock_ptr;
e91467ec (Christian Borntraeger 2006-08-05 12:13:52 -0700 1931)         barrier();
c80544dc (Stephen Hemminger     2007-10-18 03:07:05 -0700 1932)         if (lock_ptr != NULL) {
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1933)                 spin_lock(lock_ptr);
^1da177e (Linus Torvalds        2005-04-16 15:20:36 -0700 1934)                 /*

so there's an argument that get_maintainer.pl should by default
ignore whitespace changes.

Re: about get_maintainer.pl not showing the original author of the modified code

[Jianyu Zhan]

On Thu, Mar 3, 2016 at 11:32 AM, Joe Perches <joe@perches.com> wrote:
> with your patch get_maintainer.pl and --git-blame gives:
>
> $ ./scripts/get_maintainer.pl ~/1.diff --git-blame
> Thomas Gleixner <tglx@linutronix.de> (commit_signer:20/19=100%,authored:7/19=37%,added_lines:73/248=29%,removed_lines:38/119=32%)
> Peter Zijlstra <peterz@infradead.org> (commit_signer:3/19=16%,authored:1/19=5%)
> Andrew Morton <akpm@linux-foundation.org> (commit_signer:3/19=16%,modified commits:2/3=67%)
> Davidlohr Bueso <dave@stgolabs.net> (commit_signer:3/19=16%,authored:3/19=16%,added_lines:113/248=46%,removed_lines:20/119=17%)
> Ingo Molnar <mingo@kernel.org> (commit_signer:2/19=11%,modified commits:2/3=67%)
> Dominik Dingel <dingel@linux.vnet.ibm.com> (authored:1/19=5%)
> Jann Horn <jann@thejh.net> (authored:1/19=5%)
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> (added_lines:29/248=12%)
> "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> (added_lines:14/248=6%,removed_lines:49/119=41%)
> Darren Hart <dvhart@linux.intel.com> (modified commits:1/3=33%)
> Stephen Hemminger <shemminger@linux-foundation.org> (modified commits:1/3=33%)
> Christian Borntraeger <borntrae@de.ibm.com> (modified commits:1/3=33%)
> linux-kernel@vger.kernel.org (open list)
>
> vs
>
> $ ./scripts/get_maintainer.pl ~/1.diff
> Thomas Gleixner <tglx@linutronix.de> (commit_signer:20/19=100%,authored:7/19=37%,added_lines:73/248=29%,removed_lines:38/119=32%)
> Davidlohr Bueso <dave@stgolabs.net> (commit_signer:3/19=16%,authored:3/19=16%,added_lines:113/248=46%,removed_lines:20/119=17%)
> Peter Zijlstra <peterz@infradead.org> (commit_signer:3/19=16%)
> Andrew Morton <akpm@linux-foundation.org> (commit_signer:3/19=16%)
> Ingo Molnar <mingo@kernel.org> (commit_signer:2/19=11%)
> Rasmus Villemoes <linux@rasmusvillemoes.dk> (authored:1/19=5%)
> Darren Hart <dvhart@linux.intel.com> (authored:1/19=5%)
> kbuild test robot <fengguang.wu@intel.com> (authored:1/19=5%)
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> (added_lines:29/248=12%)
> "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> (added_lines:14/248=6%,removed_lines:49/119=41%)


So original author's email would be spit out only if given
--git-blame, instead of by default,
which really surprises people.  Since most time we will cc original
author,  we have to use
--git-blame explicitly, thus pay the running time cost. So the runtime
 argument don't stands,
why not just enable it by default?


Regards,
Jianyu Zhan

Re: about get_maintainer.pl not showing the original author of the modified code

[Joe Perches]

On Thu, 2016-03-03 at 12:09 +0800, Jianyu Zhan wrote:
> On Thu, Mar 3, 2016 at 11:32 AM, Joe Perches <joe@perches.com> wrote:
> > 
> > with your patch get_maintainer.pl and --git-blame gives:
> > 
> > $ ./scripts/get_maintainer.pl ~/1.diff --git-blame
> > Thomas Gleixner <tglx@linutronix.de> (commit_signer:20/19=100%,authored:7/19=37%,added_lines:73/248=29%,removed_lines:38/119=32%)
> > Peter Zijlstra <peterz@infradead.org> (commit_signer:3/19=16%,authored:1/19=5%)
> > Andrew Morton <akpm@linux-foundation.org> (commit_signer:3/19=16%,modified commits:2/3=67%)
> > Davidlohr Bueso <dave@stgolabs.net> (commit_signer:3/19=16%,authored:3/19=16%,added_lines:113/248=46%,removed_lines:20/119=17%)
> > Ingo Molnar <mingo@kernel.org> (commit_signer:2/19=11%,modified commits:2/3=67%)
> > Dominik Dingel <dingel@linux.vnet.ibm.com> (authored:1/19=5%)
> > Jann Horn <jann@thejh.net> (authored:1/19=5%)
> > Sebastian Andrzej Siewior <bigeasy@linutronix.de> (added_lines:29/248=12%)
> > "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> (added_lines:14/248=6%,removed_lines:49/119=41%)
> > Darren Hart <dvhart@linux.intel.com> (modified commits:1/3=33%)
> > Stephen Hemminger <shemminger@linux-foundation.org> (modified commits:1/3=33%)
> > Christian Borntraeger <borntrae@de.ibm.com> (modified commits:1/3=33%)
> > linux-kernel@vger.kernel.org (open list)
> > 
> > vs
> > 
> > $ ./scripts/get_maintainer.pl ~/1.diff
> > Thomas Gleixner <tglx@linutronix.de> (commit_signer:20/19=100%,authored:7/19=37%,added_lines:73/248=29%,removed_lines:38/119=32%)
> > Davidlohr Bueso <dave@stgolabs.net> (commit_signer:3/19=16%,authored:3/19=16%,added_lines:113/248=46%,removed_lines:20/119=17%)
> > Peter Zijlstra <peterz@infradead.org> (commit_signer:3/19=16%)
> > Andrew Morton <akpm@linux-foundation.org> (commit_signer:3/19=16%)
> > Ingo Molnar <mingo@kernel.org> (commit_signer:2/19=11%)
> > Rasmus Villemoes <linux@rasmusvillemoes.dk> (authored:1/19=5%)
> > Darren Hart <dvhart@linux.intel.com> (authored:1/19=5%)
> > kbuild test robot <fengguang.wu@intel.com> (authored:1/19=5%)
> > Sebastian Andrzej Siewior <bigeasy@linutronix.de> (added_lines:29/248=12%)
> > "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> (added_lines:14/248=6%,removed_lines:49/119=41%)
> 
> So original author's email would be spit out only if given
> --git-blame, instead of by default,
> which really surprises people.  Since most time we will cc original
> author,  we have to use
> --git-blame explicitly, thus pay the running time cost. So the runtime
>  argument don't stands,
> why not just enable it by default?

Several reasons:

Most of the time, git history isn't used at all
because there is a specific named maintainer.

history isn't always appropriate as the original
authors email address is old and bounces

a .get_maintainer.conf file can be used to set
whatever defaults anyone prefers.