+One of the first things we might want to do with a new, unfamiliar
+repository is understand its history. The “git log” command gives us a
+view of history.
+
+ $ git log
+ commit a1a0e8b392b17caf50325498df54802fe3c03710
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 15:43:07 2005 -0700
+
+ Trim comments.
+
+ commit 72d4f10e4a27dbb09ace1503c20dbac1912ee451
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:58 2005 -0700
+
+ Get make to generate the final binary from a .o file.
+
+ commit 13ed136b983a9c439eddeea8a1c2076cffbb685f
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:43 2005 -0700
+
+ Introduce a typo into hello.c.
+
+ commit 0a633bf58b45fcf1a8299d3c82cd1fd26d3f48f2
+ Author: Bryan O'Sullivan <mpm@selenic.com>
+ Date: Fri Aug 26 01:21:28 2005 -0700
+
+ Create a makefile
+
+ commit db7117a9dd9a6e57e8632ea5848e1101eee0fbde
+ Author: Bryan O'Sullivan <mpm@selenic.com>
+ Date: Fri Aug 26 01:20:50 2005 -0700
+
+ Create a standard "hello, world" program
+
+By default, this command prints a brief paragraph of output for each
+change to the project that was recorded. In git terminology, we
+call each of these recorded events a commit.
+
+The fields in a record of output from “git log” are as follows.
+
+ * commit This field consists of a string of 40 hexadecimal characters.
+ This is a unique identifier for referring to particular commits.
+ * Author The identity of the person who authored the commit. This
+ field consist of two sub-fields for the user's name and email
+ address, (or at least an email-like idenitifer). Note that git
+ stores a separate "Committer" field for the person who commited
+ the change, (since often an author will email a change to a
+ maintainer that commits it). The "git log" command doesn't display
+ the Committer, but other git tools do.
+ * Date The date and time on which the commit was authored, (again
+ stored separately from the date the change was committed).
+ timezone in which it was created. (The date and time are displayed
+ in the timezone of the person who created the commit.)
+ * commit message The text message that the creator of the commit
+ entered to describe the commit, (generally a one-line summary
+ followed by more supporting text).
+
+The default output printed by “git log” is purely a summary; it is
+missing a lot of detail.
+
+#### 2.4.1 Commits, revisions, and talking to other people
+
+As English is a notoriously sloppy language, and computer science has
+a hallowed history of terminological confusion (why use one term when
+four will do?), revision control has a variety of words and phrases
+that mean the same thing. If you are talking about git history
+with other people, you will find that what we have called a “commit”
+is often called a "revision". In other systems, a similar notion
+is referred to as a "changeset". You might even see abbreviations of
+these terms such as "rev", "change", or even "cset".
+
+While it may not matter much what word you use to refer to the concept
+of “a commit”, it's important to know how to name “a specific
+commit”. We have already seen one means of referring to a particular
+commit, the 40-character hexadecimal string shown by "git log". These
+commit identifiers are powerful because they are permanent, unique
+identifiers that always identify the same commit in any copy of a
+repository. If two users are examining a working directory associated
+with the same commit identifier, then those two users have precisely
+the same contents in all files, and exactly the same history leading
+to that commit.
+
+So there are places where it is often important to archive the
+complete commit identifier, (perhaps in bug-tracking systems to
+indicate a specific commit that fixes a bug, for example). But often,
+in more casual settings, it's more convenient to use abbreviated
+commit identifiers. Git accept any unique prefix of a commit
+identifier, (and for reasonably-sized project the first 8 or 10
+characters are almost always unique).
+
+And unlike the permanent commit identifiers, git also provides
+transient means of identifying commits. In fact, in day-to-day use of
+git, you will probably use these names more than commit
+identifiers. One example is branch names, (such as the default
+"master" branch in any git repository), or any project-specific branch
+names such as "stable", "experimental", or "crazy-insane-changes". Git
+also provides a special name "HEAD" which always refers to the current
+branch.
+
+#### 2.4.2 Naming related commits
+
+Git offers simple ways to name revisions that are related to
+particular revisions in the history. One syntax is the ~ suffix which
+refers to the parent of a commit, or if followed by a number, to the
+Nth parent. For example, since "HEAD" refers to the most recent commit
+in the current branch, "HEAD~", refers to the previous commit, and
+"HEAD~2" refers to two commits back in the history.
+
+Another useful syntax is .. which can be used to specify a range of
+commits. So "origin..master" specifies everything that has been
+committed to master since it derived from origin.
+
+#### 2.4.3 Viewing specific revisions
+
+You can use "git log" to explore the range syntax just introduced. For
+example, to see a list of the most recent 3 revisions you can use
+"HEAD~3..", (the destination of the range is implicitly HEAD in this
+case):
+
+ $ git log HEAD~3..
+ commit a1a0e8b392b17caf50325498df54802fe3c03710
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 15:43:07 2005 -0700
+
+ Trim comments.
+
+ commit 72d4f10e4a27dbb09ace1503c20dbac1912ee451
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:58 2005 -0700
+
+ Get make to generate the final binary from a .o file.
+
+ commit 13ed136b983a9c439eddeea8a1c2076cffbb685f
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:43 2005 -0700
+
+ Introduce a typo into hello.c.
+
+#### 2.4.4 Other log filters
+
+Besides filtering by commit identifiers, git allows you to easily
+filter the log output according to which files (or directories) are
+modified by listing them after "--" wihch is necessary to distinguish
+commit names from file names:
+
+ $ git log -- Makefile
+ commit 72d4f10e4a27dbb09ace1503c20dbac1912ee451
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:58 2005 -0700
+
+ Get make to generate the final binary from a .o file.
+
+ commit 0a633bf58b45fcf1a8299d3c82cd1fd26d3f48f2
+ Author: Bryan O'Sullivan <mpm@selenic.com>
+ Date: Fri Aug 26 01:21:28 2005 -0700
+
+ Create a makefile
+
+And "git log" can also filter based on the dates at which commits were
+created:
+
+ $ git log --since="2 weeks ago" --until="yesterday"
+
+Another useful option is -n or --max-count which, unsurprisingly,
+limits the maximum number of commits to be displayed.
+
+#### 2.4.5 More detailed information
+
+While the default information printed by “git log” is useful if you
+already know what you’re looking for, you may need to see more details
+of the change, such as the "diffstat" information with --stat:
+
+ $ git log --stat --max-count=3
+ commit a1a0e8b392b17caf50325498df54802fe3c03710
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 15:43:07 2005 -0700
+
+ Trim comments.
+
+ hello.c | 8 ++------
+ 1 files changed, 2 insertions(+), 6 deletions(-)
+
+ commit 72d4f10e4a27dbb09ace1503c20dbac1912ee451
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:58 2005 -0700
+
+ Get make to generate the final binary from a .o file.
+
+ Makefile | 2 ++
+ 1 files changed, 2 insertions(+), 0 deletions(-)
+
+ commit 13ed136b983a9c439eddeea8a1c2076cffbb685f
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:43 2005 -0700
+
+ Introduce a typo into hello.c.
+
+ hello.c | 2 +-
+ 1 files changed, 1 insertions(+), 1 deletions(-)
+
+Or perhaps you'd like to see the actual patch content of each change,
+which you can get with -p. That commit with the word typo in its name
+looks suspicous, so let's tak a closer look. Remember that we can name
+it as master~3, HEAD~3, or any prefix of its commit identifier, (such
+as 13ed136b):
+
+ $ git log -p -n 1 13ed136b
+ commit 13ed136b983a9c439eddeea8a1c2076cffbb685f
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:43 2005 -0700
+
+ Introduce a typo into hello.c.
+
+ diff --git a/hello.c b/hello.c
+ index ed55ec0..80b260c 100644
+ --- a/hello.c
+ +++ b/hello.c
+ @@ -11,6 +11,6 @@
+
+ int main(int argc, char **argv)
+ {
+ - printf("hello, world!\n");
+ + printf("hello, world!\");
+ return 0;
+ }
+
+Of course, wanting to see all this information for a single commit is
+such a common operation that it's given its own name in git, "git
+show". So "git show 13ed136b" is a much easier way to get exactly the
+same output:
+
+ $ git show 13ed136b
+ commit 13ed136b983a9c439eddeea8a1c2076cffbb685f
+ Author: Bryan O'Sullivan <bos@serpentine.com>
+ Date: Tue Sep 6 13:15:43 2005 -0700
+
+ Introduce a typo into hello.c.
+
+ diff --git a/hello.c b/hello.c
+ index ed55ec0..80b260c 100644
+ --- a/hello.c
+ +++ b/hello.c
+ @@ -11,6 +11,6 @@
+
+ int main(int argc, char **argv)
+ {
+ - printf("hello, world!\n");
+ + printf("hello, world!\");
+ return 0;
+ }