[BUG] Git merge produces inconsistent indentation in merged result

[Guo Tingsheng <CoriCraft16@xxxxxxxxxxx>]

Hello Git developers,

I would like to report a potential formatting issue I encountered when testing Git merges.

Environment:
- git version: 2.43.0
- OS: Ubuntu 24.04 LTS 

Steps to reproduce:
1. Start from a commit containing the following method:

   public void process() {
       if (flag) {
           execute();
       }
   }

2. On branch A, modify the code by adding a new conditional block with indentation consistent with the surrounding style:

   public void process() {
       if (flag) {
           execute();
       }
       if (shouldLog) {
           logger.log("Action executed.");
       }
   }

3. On branch B, make no changes to this function.

4. Merge branch A and branch B using:
   git merge A

Expected result:
- The merged file should retain the indentation style introduced by branch A:

   public void process() {
       if (flag) {
           execute();
       }
       if (shouldLog) {
           logger.log("Action executed.");
       }
   }

Actual result:
- Git reduces the indentation of the newly added lines, producing inconsistent formatting:

   public void process() {
       if (flag) {
           execute();
       }
   if (shouldLog) {
       logger.log("Action executed.");
   }
   }

Additional information:
- This issue appears to occur non-deterministically across different test cases.
- It does not seem related to core.whitespace or space-change options, but instead to how Git decides indentation for newly introduced blocks.
- The problem was reproduced using multiple merge strategies (ort, recursive).

Thanks,
Cori