hi everybody,
I am the maintainer of cregit. We are trying to improve blame traceability at the token level (see https://github.com/dmgerman/papers/blob/master/editorials/cregit/cregit.org)
We use git-blame heavilty in cregit. One of the features that I would like to add to cregit is the ability track movement of code.
I have been testing git-blame -M -C and I found some behaviour that seems incorrect. I have created a very simple repository that I think showcases this problem:
https://github.com/dmgerman/testBlameMove
this repo have 4 commits (listed below in order of execution):
1. A file is created tpm-dev.c (authored by D German), 2. a refactoring (code is moved from tpm-dev.c to tpm-dev-common.c, a new file). Author is "refactor" 3. a commit that adds some few contiguous lines (the existence of this commit seems to matter). Author is "none" 4. a commit that changes few lines and alters the result of blame for lines not modified by this commit. Author is "problem"
See below. I am running blame at different commits, showing only the lines attributed to author "refactor" (author of commit #2).
dmg@iodine:/tmp/testRepo|master ⇒ git log --oneline ded1aa1 (HEAD -> master, origin/master) problematic commit 3720e68 simple commit 391adba refactoring 33165cb file before refactoring
if we checkout 391adba and do blame -M -C we get this:
dmg@iodine:/tmp/testRepo|3720e68 ⇒ git checkout 3720e68 && git blame -M -C tpm-dev-common.c | grep refactor | head HEAD is now at 3720e68 simple commit 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 24) begin_include 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 25) include|# 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 26) directive|include 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 27) file|"tpm-dev.h" 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 28) end_include 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 147) DECL|function|tpm_common_open (struct file * file,struct tpm_chip * chip,struct file_priv * priv) 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 148) name|void 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 149) name|tpm_common_open 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 150) parameter_list|( 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 151) name|struct
so far, so good. blame detects the movement. Note that the changes by refactor are adding 5 lines (24 to 28) and then adding some at 147 and beyond.
now do it for the next commit: 3720e68
things continue to look good. The changes of this commit do not affect any of these lines.
now... the next commit, the problematic: ded1aa1 (author is not refactor)
dmg@iodine:/tmp/testRepo|3720e68 ⇒ git checkout ded1aa1 && git blame -M -C tpm-dev-common.c | grep refactor | head Previous HEAD position was 3720e68 simple commit HEAD is now at ded1aa1 problematic commit 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 24) begin_include 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 25) include|# 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 26) directive|include 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 27) file|"tpm-dev.h" 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 28) end_include 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 29) 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 30) begin_function 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 53) name|user_read_timer 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 54) argument_list|) 391adba4 tpm-dev-common.c (refactor 2018-12-06 12:41:10 -0800 150) DECL|function|tpm_common_open (struct file * file,struct tpm_chip * chip,struct file_priv * priv)
now blame assigns the lines 29, 30, 53 and 54 to commit 391adba4 refactor!!! This is what I think is a bug. (by the way, the changes made in this last commit were between 28 and 150)
thank you in advance for any clues on why git-blame is behaving like this.
--dmg
--- D M German http://turingmachine.org