How to compare files from two different branches

Question

I have a script that works fine in one branch and is broken in another. I want to look at the two versions side-by-side and see what's different. Is there a way to do this?

To be clear I'm not looking for a compare tool (I use Beyond Compare). I'm looking for a Git diff command that will allow me to compare the master version to my current branch version to see what has changed. I'm not in the middle of a merge or anything. I just want to say something like

git diff mybranch/myfile.cs master/myfile.cs

Answer 1

git diff can show you the difference between two commits:

git diff mybranch master -- myfile.cs

Or, equivalently:

git diff mybranch..master -- myfile.cs

Note you must specify the relative path to the file. So if the file were in the src directory, you'd say src/myfile.cs instead of myfile.cs.

Using the latter syntax, if either side is HEAD it may be omitted (e.g., master.. compares master to HEAD).

You may also be interested in mybranch...master (from git diff documentation):

This form is to view the changes on the branch containing and up to the second <commit>, starting at a common ancestor of both <commit>. git diff A...B is equivalent to git diff $(git-merge-base A B) B.

In other words, this will give a diff of changes in master since it diverged from mybranch (but without new changes since then in mybranch).

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In all cases, the -- separator before the file name indicates the end of command line flags. This is optional unless Git will get confused if the argument refers to a commit or a file, but including it is not a bad habit to get into. See Dietrich Epp's answer to Meaning of Git checkout double dashes for a few examples.

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The same arguments can be passed to git difftool if you have one configured.

Answer 2

You can do this: git diff branch1:path/to/file branch2:path/to/file

If you have difftool configured, then you can also: git difftool branch1:path/to/file branch2:path/to/file

Related question: How do I view 'git diff' output with my preferred diff tool/ viewer?

Answer 3

More modern syntax:

git diff ..master path/to/file

The double-dot prefix means "from the current working directory to". You can also say:

• master.., i.e. the reverse of above. This is the same as master.
• mybranch..master, explicitly referencing a state other than the current working tree.
• v2.0.1..master, i.e., referencing a tag.
• [refspec]..[refspec], basically anything identifiable as a code state to Git.

Answer 4

There are many ways to compare files from two different branches:

• Option 1: If you want to compare the file from n specific branch to another specific branch:

  git diff branch1name branch2name path/to/file
  

  Example:

  git diff mybranch/myfile.cs mysecondbranch/myfile.cs
  

  In this example you are comparing the file in “mybranch” branch to the file in the “mysecondbranch” branch.

• Option 2: Simple way:

   git diff branch1:file branch2:file
  

  Example:

   git diff mybranch:myfile.cs mysecondbranch:myfile.cs
  

  This example is similar to the option 1.

• Option 3: If you want to compare your current working directory to some branch:

  git diff ..someBranch path/to/file
  

  Example:

  git diff ..master myfile.cs
  

  In this example you are comparing the file from your actual branch to the file in the master branch.

Answer 5

If you want to make a diff against the current branch you can commit it and use:

git diff $BRANCH -- path/to/file

This way it will diff from the current branch to the referenced branch ($BRANCH).

Answer 6

I simply do git diff branch1 branch2 path/to/file

This checks for differences between the files. Changes in branch1 would be in red. Changes in branch2 would be in green.

It's assumed that branch1 is the past and branch2 is the future. You can reverse this by reversing the order of the branches in the diff: git diff branch2 branch1

Answer 7

I am agreeing with the answer by dahlbyk. If you want the diff to be written to a diff file for code reviews, use the following command.

git diff branch master -- filepath/filename.extension > filename.diff --cached

Answer 8

There are two scenarios to compare files:

Scenario 1: Compare files at remote branches (both branches should exists in the remote repository)

Scenario 2: Compare local files (at the local working area copy) to the files at the remote repository.

The logic is simple. If you provide two branch names to diff, it will always compare the remote branches, and if you provide only one branch name, it will always compare your local working copy with the remote repository (the one you provided). You can use range to provide remote repositories.

E.g., check out a branch:

git checkout branch1

git diff branch2 [filename]

In this case, if you provide filename, it will compare your local copy of filename with the remote branch named "branch2".

git diff branch1 branch2 [filename]

In this case, it will compare filename from remote branches named "branch1" vs "branch2"

git diff ..branch2 [filename]

In this case also, it will compare filename from remote branches named "branch1" vs "branch2". So, it's the same as above. However, if you have just created a branch from another branch, say "master" and your current branch doesn't exists on the remote repository, it will compare remote "master" vs. remote "branch2".

Answer 9

In my case, I use the below command:

git diff <branch name> -- <path + file name>

This command can help you compare the same file in two different branches.

Answer 10

The best way to do it is by using git diff in the following way:

git diff <source_branch> <target_branch> -- file_path

It will check the difference between files in those branches. Take a look at this article for more information about Git commands and how they work.

Answer 11

Use commit hashes as this:

git diff <hash1> <hash2> <filename>

where hash1 can be any commit from any branch, and the same for hash2.

Answer 12

In order to compare two files in Git Bash you need to use the command:

git diff <Branch name>..master -- Filename.extension

This command will show the difference between the two files in Bash itself.

Answer 13

There is another interesting point about these various ways of doing the comparison: I want to compare a file in my current branch to the same file in another branch. If I use

git difftool otherbranch.. filespec

I end up comparing two files which are actually in my temporary folder. However, If I use

git difftool otherbranch filespec

I end up comparing a file in my temporary folder (the version on otherbranch) with the actual file in my Git folder, which a) makes it much easier to tell which is which, and b) means I can use the diff tool (Beyond Compare 4 in my case) to copy changes from my other branch into my current branch.