I have several Input Sources set up other than English in order to test IME-related features in an application I work on. I can only actually understand English; accordingly the display language I have set for macOS and the language which Git uses in my terminal is English. To be perfectly clear, if I enter any Git command in the terminal, the output is always in English.
Sublime Merge seems to use whatever language occurs first in the Input Sources list to translate Git error messages to. This is pretty annoying because it means I can’t understand the error messages that Git is outputting. If I run the same command in the terminal, the error message is displayed in English, as expected.
Note that English is marked as my Primary Language in macOS’s Language & Region preferences. I would expect Sublime Merge to use the Language & Region preferences instead of the Input Sources preferences.
If I delete all other Input Sources, then output goes back to English after I restart my computer. But I need these other Input Sources for my work, so this is not a good workaround.