How git knows that branch is up to date? `Error: There is no tracking information for the current branch.`

Question

I am curious how git knows that branch is up to date if it complaints about lack of tracking information for this branch?

git pull -v --rebase=merges
POST git-upload-pack (155 bytes)
From https://github.com/org/repo
 = [up to date]        PLTFM-541_POSTGRES_PASSWORD_is_leaked -> origin/PLTFM-541_POSTGRES_PASSWORD_is_leaked
There is no tracking information for the current branch.
Please specify which branch you want to rebase against.
See git-pull(1) for details.

    git pull <remote> <branch>

If you wish to set tracking information for this branch you can do so with:

    git branch --set-upstream-to=<remote>/<branch> PLTFM-541_POSTGRES_PASSWORD_is_leaked

From the output above we can see that my branch was bound to origin repo:

PLTFM-541_POSTGRES_PASSWORD_is_leaked -> origin/PLTFM-541_POSTGRES_PASSWORD_is_leaked

But from the next message below we see that it does not:

If you wish to set tracking information for this branch you can do so with

Answer 1

I am curious how git knows that branch is up to date if it complaints about lack of tracking information for this branch?

It does not - as you correctly wrote. You are misunderstanding the output of git.

From the output above we can see that my branch was bound to origin repo:

PLTFM-541_POSTGRES_PASSWORD_is_leaked -> origin/PLTFM-541_POSTGRES_PASSWORD_is_leaked

No, that is a misunderstanding. The full output is:

= [up to date] PLTFM-541_POSTGRES_PASSWORD_is_leaked -> origin/PLTFM-541_POSTGRES_PASSWORD_is_leaked

This output is only printed because you used git pull -v - it would not be printed without the -v. This output simply informs you that:

• during the "fetch" part of the pull, git found a remote-tracking branch "origin/PLTFM-541_POSTGRES_PASSWORD_is_leaked" in your repo
• this remote-tracking branch was synchronised with the branch "PLTFM-541_POSTGRES_PASSWORD_is_leaked" in the upstream repository "origin" (a GitHub repo)
• and that these two branches were already in sync (indicated by the "=")

This says nothing about your local branch "PLTFM-541_POSTGRES_PASSWORD_is_leaked", even though this local branch has the same name as the remote branch.

The crucial thing to understand is:

Git has local branches and remote-tracking branches. Both branches are actually stored in your local repository (so both are local in a sense), but they are still different.

However, you can "link" a local branch to a remote-tracking branch by setting a remote-tracking branch as the so-called "upstream branch" or "tracking branch" of a local branch. This is what the command git branch --set-upstream-to=... does, and what happens by default to the "master" branch when you clone a repository.

You can see this "tracking information" in the output of e.g. "git branch -vv":

$ git branch -vv
feature/do-stuff    b234657 [origin/feature/do-some-stuff] fix issues
* master            44ea3fa [origin/master] implement stuff
mylocalbranch       54ad3ea do local stuff

Here, you have three local branches: "feature/do-stuff", "master", "mylocalbranch". The first two have remote-tracking branches as their tracking/upstream branches (shown in angle brackets), the third has no upstream branch (like in your case).

For more explanation, see e.g. the Git Book, chapter 3.5 Git Branching - Remote Branches