6/1/2023 0 Comments P4merge resolve conflict![]() If a file is binary, each revision is stored in full. ![]() RCS uses the "GNU diff" algorithm to determine the differences between two versions of the same file p4d contains its own diff routine which is used by Perforce servers to determine file differences when storing deltas.īecause Perforce's diff always determines file deltas by comparing chunks of text between newline characters, it is by default only used with text files. Use of "diff" to determine file revision differences This is because the head revision is accessed much more frequently than previous file revisions if the head revision of a file had to be calculated from the deltas each time it was accessed, any SCM utilizing RCS format would run much more slowly. It is interesting to note that the full text of the first revision could be stored, with the deltas leading forward through the revision history of the file, but RCS has chosen the other path: the full text of the head revision of each file is stored, with the deltas leading backwards to the first revision. In RCS terminology, it is said that the full text of the head revisions are stored, along with the reverse deltas of each previous revision. The RCS ( Revision Control System) algorithm, developed by Walter Tichy, uses a notation for implementing this system that requires very little storage space and is quite fast. Revision two might be stored as a symbolic version of the following:Īnd revision one might be a representation of this:įrom these partial file descriptions, any file revision can be reconstructed. The head revision (foo#3) looks like this: The scheme used by most SCM systems, including Perforce, is to save only the latest revision of each file, and then store the differences between each file revision and the one previous.Īs an example, suppose that a Perforce depot has three revisions of file foo. Every revision of a particular file must be retrievable, and if each revision was stored in full, disk space problems could occur: one thousand 10KB files, each with a hundred revisions, would use a gigabyte of disk space. Only the differences between revisions are storedĪ single file might have hundreds, even thousands, of revisions. If you already understand what this means, you can skip to the next section of this chapter, as the remainder of this section explains how RCS format works. Perforce uses RCS format to store its text file revisions binary file revisions are always saved in full. RCS Format: How Perforce Stores File Revisions This can eliminate file conflicts entirely. Perforce also provides facilities for locking files when they are edited. Resolves are always performed with p4 resolve. A resolve is automatically scheduled when a submit of a changelist fails because of a file conflict the same resolve can be scheduled manually, without submitting, by syncing the head revision of a file over an opened revision within the client workspace. Resolving a file conflict is a two-step process: first the resolve is scheduled, then the resolve is performed. The resolve process allows a choice to be made: Lisa's version can be submitted in place of Ed's, Lisa's version can be dumped in favor of Ed's, a Perforce-generated merged version of both revisions can be submitted, or the Perforce-generated merged file can be edited and then submitted. Instead, the changelist is rejected and a resolve must be performed. If Perforce were to accept Lisa's version into the depot, the head revision would contain none of Ed's changes. Lisa submits a changelist with her version of foo and her submit fails.Ed submits a changelist containing foo, and the submit succeeds.Ed and Lisa both edit their client workspace versions of foo.Lisa opens the same file in her client for edit.Conflicts can occur in a number of ways, but the situation is usually a variant of the following: Locking Files to Minimize File Conflictsįile conflicts can occur when two users edit and submit two versions of the same file.Using Flags with Resolve to Automatically Accept Particular Revisions.Performing Resolves of Conflicting Files.How Do I Know When a Resolve is Needed?.Scheduling Resolves of Conflicting Files.RCS Format: How Perforce Stores File Revisions.Perforce Basics: Resolving File Conflicts
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