How do I find the commit History for Author in All Branches in Azure Devops?
If you want to view the commit history within all branches in UI page, I'm afraid to say that until now, this feature does not be supported. As you can see,it only support filter in one specified branch with UI button.
In our official feature suggestion website, here has exists such feature suggested: View history for whole GIT repository. And also, here has another feature suggestion which has been under review: Show combined git branch history, including common ancestor. I believe it will be released in the near future.
Note: You can vote and comment there. When has enough votes, the Product Group will consider it as plan.
Though it could not be achieved with UI, here has another work around you can try. You can use Rest API to filter the commit history by author within all branches.
Here is the sample:
GET https://dev.azure.com/{org name}/_apis/git/repositories/{repositoryId}/commits?searchCriteria.author={author name}&api-version=5.1
This API can list the commit records with the author filtered across All branches.