Difference between git-log and git-whatchanged?

Question

1. Given this answer to another question, and
2. given that the man pages for both git-log and git-whatchanged say they pull from git-rev-list...

...what then is the difference between the two commands? Why bother having both of them?

Thatch

A recent commit (August 2013) now clarifies the difference between the two commands, and encourages to use only git log. See my answer below – Gwendolyn

Answer 1

The commit 52f425e1 (August, 30th 2013) mentions:

Encourage new users to use 'log' instead. These days, these commands are unified and just have different defaults.

'git log' only allowed you to view the log messages and no diffs when it was added in early June 2005. It was only in early April 2006 that the command learned to take diff options.
Because of this, power users tended to use 'whatchanged' that already existed since mid May 2005 and supported diff options.

---

That is what the new version of the man page for git whatchanged will say now:

New users are encouraged to use git log instead. The whatchanged command is essentially the same as git log but defaults to show the raw format diff output and to skip merges.

The command is kept primarily for historical reasons; fingers of many people who learned Git long before git log was invented by reading Linux kernel mailing list are trained to type it.

As torek comments, the git whatchanged equivalent would be:

git log --raw --no-merges

(That would avoid this question)

Gwendolyn

Thank you for coming back and adding that. In general, I think the whole git community quite thankful for you, Charles Bailey, Jakub Narębski, and anyone else who puts this much time into the git questions on SO :). – Thatch

Probably should mention that you can use git log --raw --no-merges to get the same effect without using the nominally-deprecated command. – Smoothspoken

@Smoothspoken Thank you. I have seen https://mcmap.net/q/23017/-what-flags-need-to-be-set-on-git-log-to-make-it-have-similar-output-to-git-whatchanged/6309, so I have updated this answer accordingly. – Gwendolyn

Answer 2

In their simplest form, 'git log' shows each commit (sha, author, date, message) whereas 'git whatchanged' shows the commit plus files that changed. For example:

$ git log
commit db9f525674443314a9822a6bd6c3acce49c8f8d6
Author: ...
Date:   Wed Apr 4 22:55:33 2012 -0700

Add more

commit eed0b7aa3cad5d985b5f1d52f3c0605339c119a1
Author: ...
Date:   Tue Apr 3 20:36:04 2012 -0700

del bing/one.c

but for whatchanged:

$ git whatchanged
commit db9f525674443314a9822a6bd6c3acce49c8f8d6
Author: ...
Date:   Wed Apr 4 22:55:33 2012 -0700

Add more

:100644 100644 f2e4113... d415016... M  bar.c

commit eed0b7aa3cad5d985b5f1d52f3c0605339c119a1
Author: ...
Date:   Tue Apr 3 20:36:04 2012 -0700

del bing/one.c

:100644 000000 e69de29... 0000000... D  bing/one.c

Plenty of options exist to change the output of each command. For example 'git whatchanged -p' shows the changes in diff/patch form.

Kirima

Thank you. Is there any functionality one command can do that the other simply can't? – Thatch

It appears that the answer is 'no'. Looking at the git source code shows that the two are identical other than the default options. 'git log' will 'always show header'; 'git whatchanged' will always 1) show diff output, 2) simplify history and 3) use a raw diff format by default. – Kirima

git-whatchanged doesn't include merges by default while git-log does. I haven't found the options, if there are any, to get git-log to output the list of changed files in the same way as git-whatchanged. – Picul

@Ken - You can use git-log --stat to show a list of changed files (and IMO a nicer list than git-whatchanged, since it shows the number of changed lines and supports color). – Engracia

What does the :100644 100644 f2e4113... d415016... portion just before the filename represent? – Hell

@Hell That looks like :oldmode newmode oldobjecthash newobjecthash. – Stan

Answer 3

I don't totally agree. Can you see merge changed files with log?

I didn't find this functionality and is very useful for to know when a file was merged in some branch, example:

file c.c in branch1 has a commit date from 1/1/2012, if you do a merge to branch2, and later would like to follow the day that that commit was introduced in branch2, can git log help? If you have the merges you could search in them with git whatchanged -m sha1

Longsighted