Copyright (C) 2007 - 2012 Stephen Leake Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''.
--- The Detailed Node Listing ---
Common Errors and Solutions
DVC is a common interface to several extremely powerful and flexible version control systems, such as Gnu arch, monotone, bzr, and others (known as 'backends' to DVC).
DVC provides the same (or at least similar) user interface for each backend, making it easier to use multiple backends in related projects. It also automates some tasks, and provides guidance to the user as to what needs to be done.
DVC is not included with the standard Gnu emacs distribution. It is provided in source form via a bzr repository (see Installing).
If you are not already familiar with version control systems, please read Basic DVC.
One of the most important features of the DVC user interface is that it identifies what files in a project need attention of some sort; you have changed them in your working directory, or someone else has changed them in the repository, or they've been deleted or are new, etc. DVC presents a list of all such files, and makes it easy to see what needs to be done for each file.
When committing files, ediff is used to allow reviewing the changes, so an appropriate change comment can be written.
DVC replaces the command-line interface to the backends for the most common operations, but it is still necessary to use the command line at times. Creating a repository, starting a project in a repository, and managing branches require command line operations.
This manual describes the DVC user interface, and gives examples of some required command line operations, using the monotone backend.
It also describes some DVC extensions that are specific to the monotone backend.
Here we give a brief introduction to general concepts of distributed version control systems, focusing on the concepts that are needed to use DVC, and providing common terminology.
Each backend will have its own documentation, and terminology that differs from this. The terms here are taken mostly from the monotone backend.
Let's start with some definitions:
A database can store any number of branches.
This is how changes in a development branch are promoted to the main branch.
Since propagating is a form of merging, it can encounter all of the
same conflicts that merging can.
The name of the buffer is not literally *dvc-status*; instead,
dvc is replaced by the backend name; xmtn for monotone,
bzr for bzr, etc. But in this document, we will use the name
Users edit files in their workspace, then use DVC to synchronize the workspace with the local database. Later, they use the command line to synchronize their local database with a remote database. This allows each user to make changes locally but still under change control, without affecting other users until they each choose to synchronize.
Since many people are familiar with the CVS version control system, we compare that with DVC, and monotone in particular.
In CVS, each file is committed separately; in DVC, all files in a workspace are committed together. This makes sure that all changes that are related are committed together.
This means the commit log message mentions all files that have changes; it is a much longer message, but there are fewer of them, and the message can more easily describe changes that affect more than one file.
In CVS, you must always have access to the remote server. In DVC, you work with a local database, then separately sync that database with a remote server. Thus DVC is useful when not on a network; monotone can even sync via USB disk rather than a network connection.
This means there are two steps to syncing a workspace with the central server, which can be annoying. On the other hand, the sync process syncs all projects in the database at once; with monotone, it lets you know what projects have changes.
Otherwise the primary Emacs interface to CVS and DVC are very similar, although DVC has many secondary interfaces that CVS does not have.
Install bzr; see http://bazaar.canonical.com/en/.
Retrieve the DCV source; see https://gna.org/projects/dvc#options for general information.
In a bash shell:
cd ~ bzr get http://bzr.xsteve.at/dvc/ cd ~/dvc autoconf ./configure make
In your .emacs, add
(load-file (expand-file-name "~/dvc/dvc-load.el"))
Before invoking DVC, you may want to ensure that the local database is synchronized with the central database, via a backend-specific command line.
You typically invoke DVC with the Emacs command dvc-status or dvc-diff. This prompts for a workspace; it should be the top level directory in your working directory tree.
You can also create shortcuts in text files to invoke dvc:
(dvc-status (expand-file-name "~/dvc")) (dvc-diff nil (expand-file-name "~/dvc"))
These can be executed with <C-x C-e>, and are a handy way of keeping track of several workspaces.
dvc-status or dvc-diff run the corresponding backend command, comparing the workspace against the local database, and presenting the information in the *dvc-status* or *dvc-diff* buffer.
For monotone, there are higher-level starting points:
Summarizes the status of one workspace, in a xmtn-multi-status buffer. The branch name is shown, followed by possible appropriate actions. As each action is performed, it is replaced by the next action, until there are none left.
Similarly, xmtn-status-multiple shows the status of all workspaces immediately under a root directory.
Actions are invoked with <M-d>.
The possible actions are:
xmtn-propagate-one supervises the process of propagating from one workspace to another, in an xmtn-propagate buffer.
The display shows one source and destination branch pair, and possible appropriate actions. As each action is performed, it is replaced by the next action, until there are none left.
Similarly, xmtn-propagate-multiple supervises the propagation of all workspaces immediately under two root directories. This is useful when several related projects branch together.
In the list of actions, “from” stands for the name of the source branch, “to” the name of the destination branch.
Actions are invoked with <M-d>.
The possible actions are:
xmtn-sync-review supervises the process of updating local workspaces after a command line operation that synchronizes the local and remote databases.
The command line operation should redirect stdout to ~/.dvc/sync.basic_io. Most users will want to define shell functions to invoke common syncs. For example:
mtn --db ~/monotone-dbs/gds.db automate sync --ticker=count "ssh:user@host/gds.db?*" >> ~/.dvc/sync.basic_io
The xmtn-sync-review display shows each branch that was transferred, with a count of how many revisions were sent and received.
The user may set the variable
xmtn-sync-sort to a function that
indicates how to order the branches in the display.
Actions on branches are invoked with <M-d>.
The possible branch actions are:
The user may set the variable
xmtn-sync-guess-workspace to a
function that returns a workspace given a branch. Otherwise, the user
is prompted for the workspace location; the location is cached for
Branches that are not cleaned are cached; they will reappear the next
xmtn-sync-review is run.
In addition, there are global actions:
After invoking dvc-status, you are presented with the *dvc-status* buffer.
The detailed format differs depending on the backend. This presentation is close to the bzr and mtn formats.
The buffer contains a header, such as:
Status for c:/Projects/GDS/common/main/: base revision : e946839c833b15e6bf12bd1536764e1106c41924 branch : common.main branch is merged base revision is a head revision
The last two lines are important; either may have “not” in it.
If the branch is not merged, it must be merged before an update can be done; see Merging. However, commits can be done when the branch is not merged; this allows saving work before attempting the merge.
If the base revision is not a head revision, there are updates that need to be applied to the workspace. The updates may be reviewed first using <M m>; they may be applied using <M u>.
In the main body of the buffer, there is one line for each file in the workspace that needs attention. For example:
* modified hardware/gds-hardware-pmrd_wrapper.adb unknown build/ip1k110_quartus/serv_req_info.txt E modified hardware/test/test_hardware-one_harness.adb
Each line has three fields:
Excluded files are under configuration management, but are excluded
from commits. This is used for files that each user modifies, such as
development test drivers.
In addition, some files will have extra status information that appears on the next line, indented.
The following table defines each status phrase, and gives the set of actions that can be taken for each. The action shown is from the DVC menu; the equivalent key is also given.
Other actions (such as commit) apply to all files; they are discussed later.
This status does not appear with the monotone back-end.
M-x smerge-ediff. Execute
M-x dvc-resolvewhen finished to inform the back-end that the conflict is resolved.
dvc-status-display-knownto nil. There are no appropriate actions.
Changes are committed all at once; the set of changes to the entire
workspace is called a “revision”. <c> opens the
*dvc-log-edit* buffer, where you can write a change comment.
Then <C-c C-c> commits all changes.
The key <M-d> invokes a function called “Do the Right Thing”. If there is only a single choice (or an extremely common choice) in the table above, it does that action. Otherwise, it presents a short list of the actions, in the message buffer, reminding the user of the appropriate options. Note that <M-d> means meta-d (alt-d on most PC keyboards))
Here is a summary of the most useful key bindings in the various buffers associated with DVC.
*dvc-log-edit*buffer to accumulate comments for a commit.
*dvc-log-edit*for the current diff.
In an Ediff control buffer (the small window with Ediff in the title bar):
*dvc-log-edit*for the current diff.
*xmtn-conflicts*buffer. The conflicts file and associated resolution files are saved.
To preview updates before applying them to your workspace, use the
dvc-missing command; it's on the status buffer menu at
DVC | Merge/Update | show missing.
dvc-missing can also be invoked via the Emacs command line
(<M-x>); that prompts for a local tree.
dvc-missing brings up an
showing revisions that are in your local database but not yet applied
to the workspace.
The revisions are listed oldest first.
You can view the changes made in a single revision, or from that revision to the current workspace.
See See Log edit keys, for key bindings.
<=> and <C-=> bring up a
*dvc-diff* buffer for the
revision selected. The diffs are shown in Gnu diff format; all files
*dvc-diff* buffer. There is a list of the files at the
top of the buffer. See See DVC diff keys, for key bindings.
Note that you can also review updates after they have been applied. This is often more useful, because you can edit the workspace file to fix problems caused by the update, or just to see the final state after all revisions have been applied.
Monotone allows multiple people to each commit to their local database. Then when the databases are synced, there are multiple heads for the branch; one head for each developer that commited since the last sync.
These multiple heads must be merged before a local workspace can be updated to the head of the branch; there must be only one head to update to. The monotone command line allows updating to one head of an unmerged branch, but DVC does not support this.
When the changes in the different heads are to different files, or to different parts of the same file, monotone can perform the merge itself. However, when there are changes to the same parts of one file, it needs help; this is called a content conflict.
*xmtn-conflicts* buffer shows all conflicts in a merge or
propagate. You can work thru the list one a time, using <M-d>
to specify conflict resolutions. The list is saved in a file, so you
can come back to it later.
The conflicts that monotone knows how to resolve internally have
resolved-internal; the others have no
The conflicts file and associated resolution files are stored in the monotone bookkeeping area. They must be deleted when you are done with them; use <C C> for that.
<M-d> prompts with a list of appropriate resolutions for the current conflict; select the appropriate resolution by number. The possible resolutions are:
The other side must be dropped or renamed.
The other side must be dropped or renamed.
The other side must be dropped or renamed.
See See mtn conflicts keys, for a summary of key bindings.
Sometimes, especially over NFS, the Emacs DVC interface can be painfully slow, and it is appropriate to use the mtn command line instead.
Other times, the mtn command line is just simpler.
So we list the most useful mtn commands here. See the monotone command line help or manual for more information.
mtn commit --message="<message>"
mtn commit --message-file=_MTN/log
mtn rename <file> <new-file>
mtn update --move-conflicting-paths
Problem: When attempting to update a directory, this warning appears:
$ mtn update ... mtn: warning: attach node 2147486644 blocked by unversioned path '<file path>' mtn: misuse: 1 workspace conflict
Explanation: "Unversioned path" means the indicated file is not in the current revision, however the file already exists on the disk. The revision you are updating to contains the file, but it can't be updated because it would overwrite the unknown file on the disk
Solution: Delete the indicated files from the disk and retry the update, or specify the --move-conflicting-paths option.
Problem: When attempting to propagate from one branch to another, this message appears:
$ mtn: propagating common.main -> common.work_user mtn: [left] 48b675060af47a02bc6f773bd63647726f96cbd5 mtn: [right] 94ffd0b529dfb44c3ab122fe6c514b5f2e857104 mtn: misuse: left revision id does not match conflict file
Explanation: It means you have some conflict files left over from a previous propagation or merge.
Solution: In a buffer showing the “from” workspace, run: M-x xmtn-conflicts-clean. Repeat in the “to” workspace, then propagate again.
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