What is the relationship between workspace and working directory

问题

I've been reading about Perforce but haven't found any comprehensive explanation of relationship between workspace and working directory, e.g. how files appear in working directory from workspace, how they are tracked, what inconsistencies are possible between workspace files and working directory files etc.

I come from git background, and so I'm looking for the description of workspace and working directory interaction similar to index and working directory interaction in git.

回答1:

For comprehensive information, the full Perforce documentation is available online. But here's a basic summary of the terms and concepts:

1. Perforce is a client-server system. The server tracks changes to files. Developers perform modifications to files using copies of those files on their machines, arrange those modifications into units called changelists, and submit those changelists to the server when they are ready.
2. All information about files is stored on the server. A client, or workspace, is a set of configuration data about a single copy of versioned files stored on a developer's workstation. For each workspace, the server keeps track of: which files are currently sync'd to that workspace, which pending changelists are being constructed, which user is using those files, in which directory on which computer the workspace resides, etc.
3. Getting a copy of versioned files into your workspace is called sync; submitting a new changelist with new file versions is called submit. As other users submit modifications of files, your workspace gradually becomes out of date; to bring it up to date you issue the sync command, possibly followed by the resolve command to merge newly-submitted changes to files you have been editing.
4. There isn't an exact analog of the git index construct. Modified files are copied from the developer's workspace on their workstation to the server by the submit command, and then are stored permanently in the server's archives. A somewhat different workflow is available in Perforce called a shelf. You can construct a changelist with modifications, and then use the shelve command to store that pending changelist on the server in shelved state. Pending and shelved changelists have several similarities to the way that git add allows you to assemble a commit prior to committing it, but there are also a number of differences, starting with the fact that Perforce tracks that information on the server, not in the client.

回答2:

Perfore does not really have the concept of the "index/staging area" that Git does. Files only exist within the Perforce server (the depot) or in your local working directory.

The workspace is just a bundle of configuration data that tells Perforce what files to put where in your local environment.

It is effectively a "binding" that specifies what files to select from the depot and where to place them in your working directory. This flexibility can be incredibly useful in some circumstances, but it is also an extra level of indirection compared to other VCS's such as Git/Mercurial/Subversion.

If you look at the contents of a workspace definition you will see a "Root:" section that points to a location on your local machine, and a "View:" section that tells Perforce what files you want synced to that location.

The Perforce documentation is a bit confusing with regards to its terminology. In the docs I've seen, "Workspace" refers to BOTH the specific workspace definition that you create (which is a data structure held within the Perforce server) AND the local working directory that the workspace is bound to, fairly interchangably. This is because the whole point of a workspace is to bind to a specific local working directory.

Take a look at example 15 here: Managing files and changelists

The output of the p4 sync command shows that it is writing files to the C: drive. When you "retrieve files from the depot into your client workspace" that DOES actually mean that files get copied into your local working directory.

回答3:

Let's take a workspace definition for example. The key fields for this explanation are Client, Root, and View, so I'll only show those for clarity:

Client: mysimpleclient

Root:   /Users/johndough/myspecialproject

View:
    //depot/foo/... //mysimpleclient/...

The Client field defines the name of the workspace. The Root field defines the root of the workspace on the local filesystem. The View field describes how files from the server will be mapped to your workspace files. (This adds some flexibility when compared to Git, but at the cost of a bit of a learning curve). I've used a very simple mapping here, but this could be a lot more complex.

Let's break down the View field. Let's say the server has a file //depot/foo/bar.txt.

When you sync (get latest revision) of this file, Perforce will use the view line to determine where the file lands on your filesystem.

Here is our view again: //depot/foo/... //mysimpleclient/...

The left side is in depot syntax, the right side is in workspace syntax, and it always starts with //workspace_name. The "..." is a recursive wildcard (kind of like ** with globbing). You can mentally replace the workspace name with the value of the root, to make sense of this.

Remember our root is: /Users/johndough/myspecialproject

So, after replacing "//mysimpleclient" with that value we arrive to: //depot/foo/... /Users/johndough/myspecialproject/...

Let's use that modified view line to figure out where bar.txt will end up:

//depot/foo/bar.txt /Users/johndough/myspecialproject/bar.txt

This is how it works when you pull files down. When you add new files, the mapping is read in reverse. Let's say you create a file /Users/johndough/myspecialproject/fred/file.txt

Our (mentally modified) view is: //depot/foo/... /Users/johndough/myspecialproject/...

We interpret this in reverse. Concatenate the relative path of the new file with the root of the workspace: /Users/johndough/myspecialproject/fred/file.txt

And then do the same for the left side: //depot/foo/fred/file.txt

Putting it altogether:

//depot/foo/fred/file.txt /Users/johndough/myspecialproject/fred/file.txt

Hopefully this helps. The notion of workspaces is probably the most difficult aspect of getting started with Perforce. Happy coding!

来源：https://stackoverflow.com/questions/36395820/what-is-the-relationship-between-workspace-and-working-directory