Check out git-author

[xmeng <xmeng@cs.wisc.edu>]

Hi all,

I have been using git-blame to track who changed a line of code or who 
to blame for a line of code. It is easy to use. For example, for this 
particular line of code:

$ git blame -L 2235,2235 fs/ext4/mballoc.c
85556c9a (Wei Yongjun 2012-09-26 20:43:37 -0400 2235)   
meta_group_info[i] = kmem_cache_zalloc(cachep, GFP_KERNEL);

The problem with git-blame is that it only reports the last 
author/commit that changed the line, regardless of the magnitude of the 
change. Sometimes, the last author may only change a tiny part of the 
code and should not be blamed. I developed a built-in tool called 
"git-author" to address this problem. Git-author is designed to track 
the complete development history of a line. For the same line of code:

$ git author -c -L 2235,2235 fs/ext4/mballoc.c
        CURRENT LINE 2235:       meta_group_info[i] = 
kmem_cache_zalloc(cachep, GFP_KERNEL);
85556c9 Wei Yongjun     :       meta_group_info[i] = 
kmem_cache_zalloc(cachep, GFP_KERNEL);
fb1813f Curt Wohlgemuth :       meta_group_info[i] = 
kmem_cache_alloc(cachep, GFP_KERNEL);
5f21b0e Frederic Bohe   :       meta_group_info[i] = kzalloc(len, 
GFP_KERNEL);
c9de560 Alex Tomas      :               meta_group_info[j] = 
kzalloc(len, GFP_KERNEL);

Git-author shows the complete development history of this line code. We 
can see "Wei Yongjun" only changed the line to call a different function 
(from "kmem_cache_alloc" to "kmem_cache_zalloc"). "Wei yongjun" is not 
responsible for the other part of the line. "Curt Wohlgemuth" changed 
the line to call a different function (from "kzalloc" to 
"kmem_cache_alloc") and to use a different parameter (from "len" to 
"cachep") and "Frederic Bohe" changed the line to use a different array 
index (from "i" to "j").

Git-author should be useful to people who wants to see the complete 
history of lines of code.

If you are interested in git-author, you can check it out at 
https://github.com/mxz297/git/tree/git-author (please check out branch 
'git-author'). Also we have a paper describing more technical details 
about git-author in ICSM 2013 
(ftp://ftp.cs.wisc.edu/paradyn/papers/Meng13Authorship.pdf).

Let me know if you have any question, feedback, bug about git-author!


Thanks

--Xiaozhu