Differences between revisions 6 and 22 (spanning 16 versions)
Revision 6 as of 2006-12-19 19:41:13
Size: 6001
Editor: mpm
Comment:
Revision 22 as of 2008-06-11 14:48:41
Size: 7091
Editor: garm
Comment:
Deletions are marked like this. Additions are marked like this.
Line 1: Line 1:
Mercurial's decentralized development model can be confusing to new users. This page attempts to illustate some of the basic concepts. Mercurial's decentralized development model can be confusing to new users. This page attempts to illustrate some of the basic concepts.
Line 4: Line 4:
''(Translations:
[:BrazilianPortugueseUnderstandingMercurial:Brazilian Portuguese],
[:ChineseUnderstandingMercurial:Chinese],
[:FrenchUnderstandingMercurial:French],
[:GermanUnderstandingMercurial:German],
[:ItalianUnderstandingMercurial:Italian],
[:JapaneseUnderstandingMercurial:Japanese],
[:KoreanUnderstandingMercurial:Korean],
[:RussianUnderstandingMercurial:Russian],
[:SpanishUnderstandingMercurial:Spanish]
)''

Line 8: Line 21:
Mercurial repositories contain a working directory coupled with a store: Mercurial [:Repository:repositories] contain a [:WorkingDirectory:working directory] coupled with a store:
Line 34: Line 47:
The store contains the '''complete''' history of the project. Unlike traditional SCMs, where there's only one central copy of this history, The store contains the '''complete''' history of the project. Unlike traditional [:SCM:SCMs], where there's only one central copy of this history,
Line 37: Line 50:
The working directory contains a copy of the project's files at a given point in time (eg rev 2), ready for editing. Because tags and ignored files are revision-controlled, they are also included. The working directory contains a copy of the project's files at a given point in time (eg rev 2), ready for editing. Because [:Tag:tags] and ignored files are revision-controlled, they are also included.
Line 41: Line 54:
When you '''commit''', the state of the working directory relative to its parents is recorded as new revision: When you [:Commit:commit], the state of the working directory relative to its [:Parent:parents] is recorded as a new [:Revision:revision]:
Line 70: Line 83:
Note here that revision 4 is a '''branch''' off revision 2, which was the revision in the working directory. Now revision 4 is the working directory's '''parent'''. Note here that revision 4 is a '''[:Branch:branch]''' of revision 2, which was the revision in the working directory. Now revision 4 is the working directory's '''parent'''.
Line 74: Line 87:
Mercurial groups related changes to multiple files into single atomic '''changesets''', which are '''revisions''' of the whole project.
These each get a sequential revision number. Because Mercurial allows distributed parallel development, these revision numbers may disagree between users. So Mercurial also assigns each revision a global '''changeset ID'''. Changeset IDs are 40-digit hexadecimal numbers, but they can be abbreviated to any unambiguous prefix, like "e38487".
Mercurial groups related changes to multiple files into single atomic [:ChangeSet:changesets], which are revisions of the whole project.
These each get a sequential [:RevisionNumber:revision number]. Because Mercurial allows distributed parallel development, these revision numbers may disagree between users. So Mercurial also assigns each revision a global [:ChangeSetID:changeset ID]. Changeset IDs are 40-digit hexadecimal numbers, but they can be abbreviated to any unambiguous prefix, like "e38487".
Line 91: Line 104:
Branches and merges in the revision history can occur at any point. Each unmerged branch creates a new '''head''' of the revision history.
Here, revisions 5 and 6 are heads. Mercurial considers revision 6 to be the '''tip''' of the repository, the head with the highest revision number.
Branches and [:Merge:merges] in the revision history can occur at any point. Each unmerged branch creates a new [:Head:head] of the revision history.
Here, revisions 5 and 6 are heads. Mercurial considers revision 6 to be the [:Tip:tip] of the repository, the head with the highest revision number.
Line 107: Line 120:
Bob '''clones''' this repo, and ends up with a complete copy of Alice's store (though his working directory is independent!): Bob [:Clone:clones] this repo, and ends up with a complete copy of Alice's store (though his working directory is independent!):
Line 118: Line 131:
Bob then '''commits''' a couple changes: Bob then [:Commit:commits] a couple changes:
Line 143: Line 156:
Bob then '''pulls''' Alice's repo to synchronize. This copies all of Alice's changes into Bob's repo: Bob then [:Pull:pulls] Alice's repo to synchronize. This copies all of Alice's changes into Bob's repo:
Line 158: Line 171:
Because Alice's '''g''' is the newest head in Bob's repository, it's now the '''tip'''. Bob then does a merge which combines the last change he was working on ('''f''') with the tip, commits the result, and ends up with: Because Alice's '''g''' is the newest head in Bob's repository, it's now the '''tip'''. Bob then does a [:Merge:merge] which combines the last change he was working on ('''f''') with the tip, commits the result, and ends up with:
Line 196: Line 209:
Mercurial is a completely decentralized system, and thus has no internal notion of a central repository. Thus users are free to define their own topologies for sharing changes: Mercurial is a completely decentralized system, and thus has no internal notion of a central repository. Thus users are free to define their own topologies for sharing changes (see CommunicatingChanges):
Line 215: Line 228:

== What Mercurial can't do ==

Many SVN/CVS users expect to host related projects together in one repository. This is really not what hg was made for, so you should try a different way of working. This especially means, that you cannot check out only one directory of a repository. If you absolutely need to host multiple projects in a kind of meta-repository though, you could try the ForestExtension.



For a hands-on introduction to using Mercurial, see the ["Tutorial"].

Mercurial's decentralized development model can be confusing to new users. This page attempts to illustrate some of the basic concepts. See the ["Tutorial"] for step-by-step instructions.

(Translations: [:BrazilianPortugueseUnderstandingMercurial:Brazilian Portuguese], [:ChineseUnderstandingMercurial:Chinese], [:FrenchUnderstandingMercurial:French], [:GermanUnderstandingMercurial:German], [:ItalianUnderstandingMercurial:Italian], [:JapaneseUnderstandingMercurial:Japanese], [:KoreanUnderstandingMercurial:Korean], [:RussianUnderstandingMercurial:Russian], [:SpanishUnderstandingMercurial:Spanish] )

TableOfContents

What's in a Repository

Mercurial [:Repository:repositories] contain a [:WorkingDirectory:working directory] coupled with a store:

The store contains the complete history of the project. Unlike traditional [:SCM:SCMs], where there's only one central copy of this history, every working directory is paired with a private copy of the history. This allows development to go on in parallel.

The working directory contains a copy of the project's files at a given point in time (eg rev 2), ready for editing. Because [:Tag:tags] and ignored files are revision-controlled, they are also included.

Committing Changes

When you [:Commit:commit], the state of the working directory relative to its [:Parent:parents] is recorded as a new [:Revision:revision]:

Note here that revision 4 is a [:Branch:branch] of revision 2, which was the revision in the working directory. Now revision 4 is the working directory's parent.

Revisions, Changesets, Heads, and Tip

Mercurial groups related changes to multiple files into single atomic [:ChangeSet:changesets], which are revisions of the whole project. These each get a sequential [:RevisionNumber:revision number]. Because Mercurial allows distributed parallel development, these revision numbers may disagree between users. So Mercurial also assigns each revision a global [:ChangeSetID:changeset ID]. Changeset IDs are 40-digit hexadecimal numbers, but they can be abbreviated to any unambiguous prefix, like "e38487".

Branches and [:Merge:merges] in the revision history can occur at any point. Each unmerged branch creates a new [:Head:head] of the revision history. Here, revisions 5 and 6 are heads. Mercurial considers revision 6 to be the [:Tip:tip] of the repository, the head with the highest revision number.

Cloning, Making Changes, Merging, and Pulling

Let's start with a user Alice, who has a store that looks like:

Bob [:Clone:clones] this repo, and ends up with a complete copy of Alice's store (though his working directory is independent!):

Bob then [:Commit:commits] a couple changes:

Alice then makes her own change in parallel:

Bob then [:Pull:pulls] Alice's repo to synchronize. This copies all of Alice's changes into Bob's repo:

Because Alice's g is the newest head in Bob's repository, it's now the tip. Bob then does a [:Merge:merge] which combines the last change he was working on (f) with the tip, commits the result, and ends up with:

Now if Alice pulls from Bob, she will get Bob's changes e, f, and h, and they will be fully synchronized:

A Decentralized System

Mercurial is a completely decentralized system, and thus has no internal notion of a central repository. Thus users are free to define their own topologies for sharing changes (see CommunicatingChanges):

What Mercurial can't do

Many SVN/CVS users expect to host related projects together in one repository. This is really not what hg was made for, so you should try a different way of working. This especially means, that you cannot check out only one directory of a repository. If you absolutely need to host multiple projects in a kind of meta-repository though, you could try the ForestExtension.

For a hands-on introduction to using Mercurial, see the ["Tutorial"].

UnderstandingMercurial (last edited 2013-09-02 20:00:50 by WagnerBruna)