Conflicts occur even when merging modular contributions

Only Merge Scenarios with Conflitcts

Sample	Non modular contributions (%)	Modular contributions (%)
Ruby sample	57.3	42.7
Python sample	70.8	29.2

Likelihood of conflict occurrence significantly increases when contributions to be merged are not modular

Ruby Sample (Model I) - Odds Ratios from Regression Assessing Merge Conflicts Factors

Factor Metric	Model I	Model II	Model III	Model IV	Model V	Model VI	Model VII
Changes to a common slice	6.13 ***	4.28 ***	3.80 ***	5.18 ***	4.28 ***	3.78 ***	5.11 ***
Number of commits		3.55 ***			3.53 ***
Number of developers			1.17 ***	1.56 ***		1.15 ***	1.51 ***
Number of changed files			3.27 ***			3.24 ***
Number of changed lines				0.99			0.99
Duration						1.04 ***	1.09 ***
Conclusion delay					1.01	1.01	1.01
Deviance Explained	10.9%	17.5%	19.0%	14.3%	17.5%	19.0%	14.5%

^*** p < 0.001 ^** p < 0.01 ^* p < 0.05

Python Sample (Model I) - Odds Ratios from Regression Assessing Merge Conflicts Factors

Factor Metric	Model I	Model II	Model III	Model IV	Model V	Model VI	Model VII
Changes to a common slice	4.39 ***	2.82 ***	3.13 ***	3.60 ***	2.83 ***	3.11 ***	3.52 ***
Number of commits		2.16 ***			2.17 ***
Number of developers			1.36 ***	1.45 ***		1.36 ***	1.44 ***
Number of changed files			2.40 ***			2.17 ***
Number of changed lines				1.64 ***			1.49 ***
Duration						1.18 ***	1.23 ***
Conclusion delay					0.98	0.87 ***	0.85 ***
Deviance Explained	7.1%	14.4%	13.5%	11.6%	14.4%	14.3%	12.7%

^*** p < 0.001 ^** p < 0.01 ^* p < 0.05

Contribution non modularity does not predict the extent of merge damage

Ruby Sample - Changes to a common slice does not correlate strongly with

Conflict Metric	cor *	p-value
Number of merge conflicts	0.07	< 2.2e-16
Number of files with merge conflicts	0.13	< 2.2e-16

Python Sample - Changes to a common slice does not correlate strongly with

Conflict Metric	cor *	p-value
Number of merge conflicts	0.06	7.532e-12
Number of files with merge conflicts	0.09	< 2.2e-16

* We compute the point-biserial correlation coefficient since changes to a common slice is a dichotomous variable.

Conflicts in non modular scenarios often occur in model, view, and controller files

Only conflicting scenarios with non modular contributions	% contain at least one slice file (model, view or controller) with at least one conflict
Ruby sample	62.8%
Python sample	76.9%

Most contributions involve changes to more than one MVC module

MVC modules affected by contributions	% Ruby Sample	% Python Sample
Mixed1	65.3	57.9
Config 2	23.6	22.5
App3	4.0	8.8
View4	3.3	4.0
Model5	2.1	3.8
Controller6	1.6	2.9
Total	100.0	100.0

1 - contributions affect more than one MVC module
2 - contains only configuration files such as routes, database schema, logs, Rakefile, Gemfile, etc
3 - contains only global reusable files such as CSS files, templates, static pages, and Javascript files
4 - contains only view files
5 - contains only model files
6 - contains only controller files