Tutorial - Examining Repository History
At this point, we have followed TutorialClone to clone a repository; our local copy is called my-hello.
Let's take a look at the history of this repository. To do this, we use the log command. This prints a summary of every event that has occurred in the repository, going backwards in time from the most recent.
$ hg log changeset: 1:82e55d328c8c tag: tip user: email@example.com date: Fri Aug 26 01:21:28 2005 -0700 summary: Create a makefile changeset: 0:0a04b987be5a user: firstname.lastname@example.org date: Fri Aug 26 01:20:50 2005 -0700 summary: Create a standard "hello, world" program
These lines of output bear some describing.
Each paragraph describes a particular changeset. A changeset is a modification of one or more files, grouped together into a logical unit.
- In our case above, we can see that the repository's history consists of two changesets.
changeset identifies a changeset.
The first number before the colon is a revision number; it is a local short-hand way of identifying the changeset. It is only valid within this repository.
The hexadecimal string after the colon is a short-form changeset ID; it identifies the changeset, and is the same in all repositories that contain this changeset. If you are ever discussing a changeset with someone else, use the changeset ID, not the revision number.
tag is a tag, an arbitrary symbolic name for a changeset.
You can assign one or more tags to any changeset. Actually, not that many changeset will have tags associated with them, so the tag line will seldom be present.
The special tag named tip always identifies the tip, which is the most recent changeset in the repository. If you create another changeset (and we will, soon), the tip tag will be removed from the most recent changeset and will be added to the new changeset.
user identifies the person who created the changeset. This is a free-form string; it usually contains an email address, and sometimes a person's name, too.
date describes when the changeset was created. These dates are printed in the local time zone the creator of the changeset was in.
summary gives the first line of the changeset description, entered by the changeset creator to help understand the purpose of the changeset when looking at it later (see also ChangeSetComments).
parent identifies the parent changesets, in case there are more than one, which happens when you merge changes from several locations.
- Most of the times there is only one parent, which is the one changeset older than itself. This is the case in our example above.
We can get more detailed history information by asking for verbose output with the -v option, or the --debug global option for everything under the sun:
$ hg log -v changeset: 1:82e55d328c8c tag: tip user: email@example.com date: Fri Aug 26 01:21:28 2005 -0700 files: Makefile description: Create a makefile (...) $ hg log --debug changeset: 1:82e55d328c8ca4ee16520036c0aaace03a5beb65 tag: tip parent: 0:0a04b987be5ae354b710cefeba0e2d9de7ad41a9 parent: -1:0000000000000000000000000000000000000000 manifest: 1:0c7c1d435e6703e03ac6634a7c32da3a082d1600 user: firstname.lastname@example.org date: Fri Aug 26 01:21:28 2005 -0700 files+: Makefile extra: branch=default description: Create a makefile (...)
Verbose output contains a few more fields than the default output.
files lists the files modified in this changeset.
description contains the complete multi-line description of the changeset, rather than just the first line.
- In our case, the descriptions are only one-line long, so there's not much difference.
The --debug output adds the following fields to the verbose output (see also DebuggingFeatures):
changeset now gives the unabbreviated changeset ID.
two parent fields giving the changeset ID of both parents for this changeset, where -1:0000000000000000000000000000000000000000 refers to a non-existant parent.
manifest gives the manifest ID for this changeset.
file+ lists the file(s) added in this changeset.
file- lists the file(s) removed in this changeset.
The log command comes with a -r option to view specific changesets.
$ hg log -r1 changeset: 1:82e55d328c8c tag: tip user: email@example.com date: Fri Aug 26 01:21:28 2005 -0700 summary: Create a makefile
The -r option actually supports a very flexible syntax to select a range of changesets. However, due to limited number of changesets available in our sample repository, we are unable to provide a good demonstration. Please consult the manpage for more information.
The log command also comes with a -p option to show the patches associated with the changesets:
$ hg log -r1 -p changeset: 1:82e55d328c8c tag: tip user: firstname.lastname@example.org date: Fri Aug 26 01:21:28 2005 -0700 summary: Create a makefile diff -r 0a04b987be5a -r 82e55d328c8c Makefile --- /dev/null Fri Aug 26 01:20:50 2005 -0700 +++ b/Makefile Fri Aug 26 01:21:28 2005 -0700 @@ -0,0 +1,1 @@ +all: hello
We can also use the tip command to show info of the tip, i.e. the latest, changeset. The tip command may be considered a shortcut to log -r tip.
$ hg tip changeset: 1:82e55d328c8c tag: tip user: email@example.com date: Fri Aug 26 01:21:28 2005 -0700 summary: Create a makefile $ hg log -r tip changeset: 1:82e55d328c8c tag: tip user: firstname.lastname@example.org date: Fri Aug 26 01:21:28 2005 -0700 summary: Create a makefile
Now that we have some slight idea of what has happened, let's jump in and make some changes! Onwards, to TutorialFirstChange!