GNU Emacs Manual. Node: VC Status Retrieval

PREVVC Workfile Handling UPCustomizing VC NEXTVC Command Execution VC Status Retrieval

When deducing the locked/unlocked state of a file, VC first looks for an RCS version header string in the file (see Version Headers). If there is no header string, or if you are using SCCS, VC normally looks at the file permissions of the work file; this is fast. But there might be situations when the file permissions cannot be trusted. In this case the master file has to be consulted, which is rather expensive. Also the master file can only tell you if there's any lock on the file, but not whether your work file really contains that locked version.

You can tell VC not to use version headers to determine lock status by setting vc-consult-headers to nil. VC then always uses the file permissions (if it can trust them), or else checks the master file.

You can specify the criterion for whether to trust the file permissions by setting the variable vc-mistrust-permissions. Its value can be t (always mistrust the file permissions and check the master file), nil (always trust the file permissions), or a function of one argument which makes the decision. The argument is the directory name of the `RCS', `CVS' or `SCCS' subdirectory. A non-nil value from the function says to mistrust the file permissions. If you find that the file permissions of work files are changed erroneously, set vc-mistrust-permissions to t. Then VC always checks the master file to determine the file's status.

PREVVC Workfile Handling UPCustomizing VC NEXTVC Command Execution