How does git track renames

A Git repository can store a flag to register the encoding supposedly used for comments including author names. File content is not converted unless you are inclined to want to shoot yourself in the foot, in which case use the filtering mechanism described above. Git has a specific notion of tracked "content", which is basically just the file data. See ContentLimitations for more details. The push operation is always about propagating the repository history and updating the refs, and never touches the working tree files.

In particular, if you push to update the branch that is checked out in a remote repository the files in the work tree will not be updated. This is a precautionary design decision. The remote repository's work tree may have local changes, and there is no way for you, who are pushing into the remote repository, to resolve conflicts between the changes you are pushing and the ones in the work tree.

However, you can easily make a post-update hook to update the working copy of the checked out branch. The reason for not making this a default example hook is that they only notify the person doing the pushing if there was a problem.

It also fails to work in instances where it could, such as none of the files are actually conflicting. A quick rule of thumb is to never push into a repository that has a work tree attached to it, until you know what you are doing. If you are sure what you are doing, you can do a "git reset --hard" on the side you pushed to. See this article about bare repositories for details. See also the entry How would I use "git push" to sync out of a firewalled host?

There is a bit of a chicken and egg problem involved. The build procedure wants to have an already installed Git to figure out the "full" version number. If you are bootstrapping, make clean and rebuild after you install Git once would give you a Git binary that knows what version it is. If reset switches to a version with a different. This means that your branch is not a strict superset of the remote side. That is, the remote side has commits that your side does not have. If you would push, the other side would lose changes.

The most likely reason for this is that you need to. You can see what changes the remote side has by fetching first and then checking the log. For example,. If you want a graphical representation, use gitk --left-right master The arrows to the left are changes you want to push, the arrows to the right are changes on the remote side.

Be warned that if you rewind branches, others might get into problem when pulling. There is the chance that they will merge in the branch that they fetched with the new one that you've published, effectively keeping the changes that you are trying to get rid of.

However, it will only be their copies that have the bad revisions. For this reason, rewinding branches is considered mildly antisocial. Nonetheless, it is often appropriate. After you have rebased one of your local branches, you try to push your changes to a remote repository — but git push fails with this error message:. This is not a bug, but a safety check: "git push" will not update a remote branch if the remote branch is not a parent of the commit you're trying to push.

This check prevents you from overwriting a remote branch to which other people have already committed new changes after you fetched it the last time. Their changes would be lost without the check. And it prevents you from overwriting a remote branch with an unrelated local branch. When you rebase, you are not continuing the history of the branch from where you currently are.

Instead, you are rewriting the history starting from the base you chose for rebasing. So, after rebasing, the remote branch and your new local HEAD are both child commits of that base, but the remote branch is no longer a parent of your new local HEAD.

And pushing this new history to the remote branch means replacing a history that other people might already have downloaded. If you are really sure that you want to push the new reference to the remote repository you can say git push -f.

But use this with care and only if you know what you are doing. However, recent versions of Git disable the ability to push -f by default because it is usually an error. Most other version control systems will do a full-tree commit, using the content of files at commit time, by default. Git does it differently. By default, Git commits the content of the index, and only this. Indeed, there are many concrete reasons why Git's way to manage the index is good and leads to unique features of Git :.

Indeed, according to Linus, the real reason is more philosophical: Git is a content tracker, and a file name has no meaning unless associated to its content. Therefore, the only sane behavior for git add filename is to add the content of the file as well as its name to the index.

HTTP is a "dumb" transport, which needs some help. See also git-http-backend 1. Modification time on files is a feature that affects build tools. Most build tools compare the timestamp of the source s with the timestamp of the derived file s. If the source is newer, then a rebuild takes place, otherwise nothing happens.

This speeds up the build process a lot. Now consider what would happen if you check out another branch, and modification times were preserved. We assume you already have a fully-built project. If a source file on that other branch has a timestamp that is older than that of the corresponding derived file, the derived file will not be built even if it is different, because the build system only compares modification times. At best, you'll get some kind of weird secondary error; but most likely everything will look fine at first, but you will not get the same result as you would have with a clean build.

That situation is unhealthy since you really do not know what code you are executing and the source of the problem is hard to find. You will end up always having to make a clean build when switching branches to make sure you are using the correct source.

Git bisect is another Git procedure that checks out old and new revisions where you need a reliable rebuild. Git sets the current time as the timestamp on every file it modifies, but only those. The other files are left untouched, which means build tools will be able to depend on modification time and rebuild properly. If build rules change, that can cause a failure anyway, but that is a far less common problem than accidentally not rebuilding.

Usually, you are not interested in the whole log, but only some bits at the beginning. It would not be useful for "git log" to simply let the output whiz by, leaving you looking at the uninteresting parts at the end. And if it did it the other way round, showing you the interesting bits last, it would waste a lot of time showing information that you are not interested in at all.

So the only thing that makes sense is to look at the log in a pager. It also helps searching for keywords. Note that "--help" just spawns "man", so it is not Git's fault there. But you can use git help -w xxx to use a browser instead of "man" if the HTML documentation is installed.

See the Git help documentation for more information about this. If you do not like the pager default, you can set core. Set core. The most likely culprit is the LESS environment variable. Depending on which tool you are using to inspect file history, there are various ways to include rename history. Files are not staged yet, so this is not shown as a rename.

Check this out:. We still have a deletion and an addition. Why was git able to follow move of. Rather, it sees it as a deletion of the old line, and addition of a new line.

And this applies not only to lines of code — it applies to entire files. But if this is true, then why did we see the rename as a single file marked as R in the staged git view?

And why does Git Lens show this history:. Looking in Azure DevOps will also show the file as renamed. So git must be tracking this as a rename. When trying to figure out whether there are any renames, git does some heuristics.

This is where it starts. From git perspective, file is not identified by file name only, but by file content. Whenever a file is added in git, git will calculate the hash of entire file contents.

Two files with exactly the same content will have exactly the same hash. If there is a file in both lists with the same hash, git immediately sees this as a match, and will treat this as a rename. So, even though git sees Foo. This is also blazing fast, because it only needs do compare two very short strings, and even if you have thousands of renames like, you rename an entire subtree, say from.

To do so, git will run git diff internally. Remember my example above where I not only renamed Foo. When you both do a bunch of renames and a bunch of code changes, hashes will change for a lot of those renamed files, so git will have to run git diff for all files where there is no hash match. Rename detection logic in diffcore-rename that checks for renames of individual files is also aggregated there and then analyzed in either merge-ort or merge-recursive for cases where combinations of renames indicate that a full directory has been renamed.

And perhaps the inner directory itself contained inner directories that were renamed to yet other locations. In order to prevent edge and corner cases resulting in either conflicts that cannot be represented in the index or which might be too complex for users to try to understand and resolve, a couple basic rules limit when directory rename detection applies:.

It also lists a few additional rules:. Arvind Ravichandran. Hansika Herath. RudderStack in Nerd For Tech. Erik Engheim.

Anusuya Ramasamy. Binary Search Tree Implementation in Python. Bad advice!