azure script variable not recognized

Here is my azure pipeline snippet:

- steps 
   - script : | 

         isChanged = git diff --stat abc.txt

git diff --stat abc.txt working fine. But getting isChanged is unrecognized as internal or external command

its not Linux(Bash) based shell, so got that error.

Here is the correct one. default Windows shell (cmd):

steps:
  - script: |
      REM Check if abc.txt has any changes and capture the output in a variable
      for /f "delims=" %%i in ('git diff --stat abc.txt') do set "isChanged=%%i"

      REM If there are no changes, set the pipeline variable isChanged to 'false', otherwise 'true'
      if "%isChanged%"=="" (
        echo No changes in abc.txt
        echo ##vso[task.setvariable variable=isChanged]false
      ) else (
        echo Changes detected in abc.txt
        echo ##vso[task.setvariable variable=isChanged]true
      )
    displayName: 'Check if abc.txt has changed'