Re: [PATCH v1] add status config and command line options for rename detection

[Ben Peart <peartben@gmail.com>]

On 5/9/2018 11:59 AM, Duy Nguyen wrote:
> On Wed, May 9, 2018 at 4:42 PM, Ben Peart <Ben.Peart@microsoft.com> wrote:
>> Add a new config status.renames setting to enable turning off rename detection
>> during status.  This setting will default to the value of diff.renames.
> 
> Please add the reason you need this config key in the commit message.
> My guess (probably correct) is on super large repo (how large?),
> rename detection is just too slow (how long?) that it practically
> makes git-status unusable.
> 

Yes, the reasons for this change are the same as for the patch that 
added these same flags for merge and have to do with the poor 
performance of rename detection with large repos.  I'll update the 
commit message to be more descriptive (see below) and correct some 
spelling errors.


add status config and command line options for rename detection

After performing a merge that has conflicts, git status will by default 
attempt to detect renames which causes many objects to be examined.  In 
a virtualized repo, those objects do not exist locally so the rename 
logic triggers them to be fetched from the server. This results in the 
status call taking hours to complete on very large repos.  Even in a 
small repo (the GVFS repo) turning off break and rename detection has a 
significant impact:

git status --no-renames:
31 secs., 105 loose object downloads

git status --no-breaks
7 secs., 17 loose object downloads

git status --no-breaks --no-renames
1 sec., 1 loose object download

Add a new config status.renames setting to enable turning off rename 
detection during status.  This setting will default to the value of 
diff.renames.

Add a new config status.renamelimit setting to to enable bounding the 
time spent finding out inexact renames during status.  This setting will 
default to the value of diff.renamelimit.

Add status --no-renames command line option that enables overriding the 
config setting from the command line. Add --find-renames[=<n>] to enable 
detecting renames and optionally setting the similarity index from the 
command line.

Note: I removed the --no-breaks command line option from the original 
patch as it will no longer be needed once the default has been changed 
[1] to turn it off.

[1] 
https://public-inbox.org/git/20180430093421.27551-2-eckhard.s.maass@gmail.com/

Original-Patch-by: Alejandro Pauly <alpauly@microsoft.com>
Signed-off-by: Ben Peart <Ben.Peart@microsoft.com>


> This information could be helpful when we optimize rename detection to
> be more efficient.
> 
>>
>> Add a new config status.renamelimit setting to to enable bounding the time spent
>> finding out inexact renames during status.  This setting will default to the
>> value of diff.renamelimit.
>>
>> Add status --no-renames command line option that enables overriding the config
>> setting from the command line. Add --find-renames[=<n>] to enable detecting
>> renames and optionaly setting the similarity index from the command line.
>>
>> Origional-Patch-by: Alejandro Pauly <alpauly@microsoft.com>
>> Signed-off-by: Ben Peart <Ben.Peart@microsoft.com>