Merge Conflict Resolu2on public float calculateDiscount( final float - PowerPoint PPT Presentation

Merge Conflict Resolu2on public float calculateDiscount( final float cost) { <<<<<<< HEAD return cost * 0.5f; ======= return cost / 2; >>>>>>> dev1 } SWEN-261 Introduc2on to So3ware Engineering Department of So3ware Engineering Rochester Ins2tute of Technology

Merging happens on every pull. § Every time you sync with the remote a merge occurs. • A "fast forward" is when your local branch has no additional changes and your local ref is just moved to the commit point of the remote. • If your local changes do not overlap with the changes fetched from the remote, then an automatic merge is possible. § A conflict occurs when there is at least one file with overlapping changes. 2

Here's an example of a merge conflict. § Imagine there is a bug in a method: /** * Calculate a half-off discount. */ public float calculateDiscount(final float cost) { return cost * 2; } § Independently, two developers fix this bug: • Betty did this: return cost / 2; • Sam did this: return cost * 0.5f; 3

When a conflict occurs git reports the affected files. § When Sam merges in the code from Betty: ➔ git merge dev1 Auto-merging src/main/java/com/example/model/Promotion.java CONFLICT (content): Merge conflict in src/main/java/com/example/ model/Promotion.java Automatic merge failed; fix conflicts and then commit the result. § Sam now has to fix the conflict; seen here: public float calculateDiscount( final float cost) { <<<<<<< HEAD The HEAD in Sam's workspace. return cost * 0.5f; ======= return cost / 2; This is the code from Betty's branch. >>>>>>> dev1 } 4

Resolving a simple text conflict is often easy. § Determine the best solution, and remove the other solution and the marker text. /** * Calculate a half-off discount. */ public float calculateDiscount( final float cost) { return cost / 2; } § Then add (and commit) the resolved change: git commit –am "Fixed discount calculation" § Push it. 5

There are other challenges when merging. § Binary files • Document files, such as Word or Excel, are binary and cannot be merged. • Such files should have an owner who is responsible for moderating changes. • And a clear protocol for permitting team members access. § Tree structures • Types: w file name changes w directory name changes w moving files and directories • Why: w Java package changes w Class name changes 6

To minimize the number of times when conflicts will not resolve easily, follow several guidelines. 1. Keep code lines short; break up long calculations. 2. Keep commits small and focused. 3. Minimize stray edits. 4. If multiple developers are collaborating on a feature, each developer should sync with the remote branch regularly. Merge in the remote branch and then push to it, if you have changes. 5. If development of a feature is taking a long time, merge in master to sync with completed features in this sprint. 7