Previously, I merge the branch into the master branch using git bash. When the conflict happened, I can see and solve the conflict in the visual studio. But now, don't know what is happened, git bash doesn't show the conflict in visual studio. Git bash only enters edit mode to merge the branches which I don't know how to use it. Any setting needed to set? So that I still can use visual studio to resolve the conflict in visual studio which is clearer to see the conflicts.
Provided your git config (generally, the global one: git config --global -l) does declare the Visual Studio tool as a merge tool (as in this example), you can invoke it with git mergetool ${file}:
[merge]
tool = vsdiffmerge
[mergetool]
prompt = false
[mergetool "vsdiffmerge"]
cmd = '"C:/Program Files (x86)/Microsoft Visual Studio 14.0/Common7/IDE/vsdiffmerge.exe"' "$REMOTE" "$LOCAL" "$BASE" "$MERGED" //m
keepbackup = false
trustexitcode = true