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Date:   Sun, 13 Jan 2019 08:07:04 +0100 (CET)
From:   Julia Lawall <julia.lawall@lip6.fr>
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Subject: git blame --reverse reports on lines that were not asked for
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Version: git version 2.17.1, git version 2.20.1

Git tree:
https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux-stable
7566ec393f4161572ba6f11ad5171fd5d59b0fbd

The command git blame --reverse 91e4f1b6073dd680d86cdb7e42d7cccca9db39d8..HEAD -L1176,1176 -L1173,1173 arch/mips/kvm/emulate.c

Produces:

693dfd5a3f19e (Erez Shitrit 2017-04-27 17:01:34 +0300 1173)                                     preempt_disable();
693dfd5a3f19e (Erez Shitrit 2017-04-27 17:01:34 +0300 1174)                                     /* Blow away the shadow host TLBs */

Line 1174 was not asked for, and there is no information about line 1176.

git blame --reverse 91e4f1b6073dd680d86cdb7e42d7cccca9db39d8..HEAD -L1173,1173 -L1175,1175 arch/mips/kvm/emulate.c works fine:

693dfd5a3f19e (Erez Shitrit 2017-04-27 17:01:34 +0300 1173)                                     preempt_disable();
f3124cc551c85 (James Hogan  2016-09-16 00:00:08 +0100 1175)                                     kvm_mips_flush_host_tlb(1);

git blame --reverse 91e4f1b6073dd680d86cdb7e42d7cccca9db39d8..HEAD -L1173,1176 arch/mips/kvm/emulate.c also works fine:

693dfd5a3f19e (Erez Shitrit 2017-04-27 17:01:34 +0300 1173)                                     preempt_disable();
f3124cc551c85 (James Hogan  2016-09-16 00:00:08 +0100 1174)                                     /* Blow away the shadow host TLBs */
f3124cc551c85 (James Hogan  2016-09-16 00:00:08 +0100 1175)                                     kvm_mips_flush_host_tlb(1);
693dfd5a3f19e (Erez Shitrit 2017-04-27 17:01:34 +0300 1176)                                     cpu = smp_processor_id();

My impression is that git --reverse blame is not all that reliable, and we can even see that 1174 gets assigned to two different commits depending on how the command is formulated.  But I would expect it to at least report on only and exactly the lines that were asked for.

thanks,
julia