Most useful variations of git blame, using examples from Linux kernel source.

Show the (most recent) origin of each line in a file:

$ git blame Makefile
b24413180f560 (Greg Kroah-Hartman       2017-11-01 15:07:57 +0100    1) # SPDX-License-Identifier: GPL-2.0
c517d838eb7d0 (Linus Torvalds           2015-02-22 18:21:14 -0800    2) VERSION = 4
60cc43fc88842 (Linus Torvalds           2018-04-15 18:24:20 -0700    3) PATCHLEVEL = 17
55922c9d1b84b (Linus Torvalds           2011-05-29 17:43:36 -0700    4) SUBLEVEL = 0
67b8d5c708122 (Linus Torvalds           2018-05-13 16:15:17 -0700    5) EXTRAVERSION = -rc5
75bc37fefc447 (Linus Torvalds           2018-05-06 16:57:38 -1000    6) NAME = Merciless Moray
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700    7) 
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700    8) # *DOCUMENTATION*
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700    9) # To see a list of typical targets execute "make help"
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   10) # More info can be located in ./README
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   11) # Comments in this file are targeted only to the developer, do not
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   12) # expect to learn how to build the kernel reading this file.
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   13) 
... snip ...

and once you determine the offending line, you can examine its encompassing commit with git show:

$ git show b24413180f560
commit b24413180f5600bcb3bb70fbed5cf186b60864bd
Author: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date:   Wed Nov 1 15:07:57 2017 +0100

    License cleanup: add SPDX GPL-2.0 license identifier to files with no license
    
    Many source files in the tree are missing licensing information, which
    makes it harder for compliance tools to determine the correct license.
    
    ... snip ...

A very small subset of options for git blame (there are far more):

-L <start>,<end>, -L :<funcname>
    Annotate only the given line range. May be specified multiple times.
    Overlapping ranges are allowed.

-s
    Suppress the author name and timestamp from the output.

-e, --show-email
    Show the author email instead of author name (Default: off).
    This can also be controlled via the ''blame.showEmail'' config option.