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Fix the commit hashes in ch10.2 #1422

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8a605ac
Fix the commit hashes in ch10.2
Smaug123 May 3, 2020
b2a60f9
Repair also two hashes I missed
Smaug123 May 3, 2020
dbc379a
Indicate in the refs chapter where hashes needed to change; but we st…
Smaug123 May 3, 2020
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26 changes: 13 additions & 13 deletions book/10-git-internals/sections/objects.asc
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Original file line number Diff line number Diff line change
Expand Up @@ -254,7 +254,7 @@ Start with the first tree you wrote:
[source,console]
----
$ echo 'First commit' | git commit-tree d8329f
fdf4fc3344e67ab068f836878b6c4951e3b15f3d
70d4408b5020e81d19906d6abdd87a73233ebf34
----

You will get a different hash value because of different creation time and author data.
Expand All @@ -263,7 +263,7 @@ Now you can look at your new commit object with `git cat-file`:

[source,console]
----
$ git cat-file -p fdf4fc3
$ git cat-file -p 70d4408b
tree d8329fc1cc938780ffdd9f94e0d364e0ea74f579
author Scott Chacon <[email protected]> 1243040974 -0700
committer Scott Chacon <[email protected]> 1243040974 -0700
Expand All @@ -277,19 +277,19 @@ Next, you'll write the other two commit objects, each referencing the commit tha

[source,console]
----
$ echo 'Second commit' | git commit-tree 0155eb -p fdf4fc3
cac0cab538b970a37ea1e769cbbde608743bc96d
$ echo 'Third commit' | git commit-tree 3c4e9c -p cac0cab
1a410efbd13591db07496601ebc7a059dd55cfe9
$ echo 'Second commit' | git commit-tree 0155eb -p 70d4408b
1513b13a72f5277252cfce4ed0eda0620aca2f6a
$ echo 'Third commit' | git commit-tree 3c4e9c -p 1513b13a
95cce637b4e889eee8042515db402128bd62c0d2
----

Each of the three commit objects points to one of the three snapshot trees you created.
Oddly enough, you have a real Git history now that you can view with the `git log` command, if you run it on the last commit SHA-1:

[source,console]
----
$ git log --stat 1a410e
commit 1a410efbd13591db07496601ebc7a059dd55cfe9
$ git log --stat 95cce6
commit 95cce637b4e889eee8042515db402128bd62c0d2
Author: Scott Chacon <[email protected]>
Date: Fri May 22 18:15:24 2009 -0700

Expand All @@ -298,7 +298,7 @@ Date: Fri May 22 18:15:24 2009 -0700
bak/test.txt | 1 +
1 file changed, 1 insertion(+)

commit cac0cab538b970a37ea1e769cbbde608743bc96d
commit 1513b13a72f5277252cfce4ed0eda0620aca2f6a
Author: Scott Chacon <[email protected]>
Date: Fri May 22 18:14:29 2009 -0700

Expand All @@ -308,7 +308,7 @@ Date: Fri May 22 18:14:29 2009 -0700
test.txt | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)

commit fdf4fc3344e67ab068f836878b6c4951e3b15f3d
commit 70d4408b5020e81d19906d6abdd87a73233ebf34
Author: Scott Chacon <[email protected]>
Date: Fri May 22 18:09:34 2009 -0700

Expand All @@ -328,15 +328,15 @@ Here are all the objects in the example directory now, commented with what they
----
$ find .git/objects -type f
.git/objects/01/55eb4229851634a0f03eb265b69f5a2d56f341 # tree 2
.git/objects/1a/410efbd13591db07496601ebc7a059dd55cfe9 # commit 3
.git/objects/15/13b13a72f5277252cfce4ed0eda0620aca2f6a # commit 2
.git/objects/1f/7a7a472abf3dd9643fd615f6da379c4acb3e3a # test.txt v2
.git/objects/3c/4e9cd789d88d8d89c1073707c3585e41b0e614 # tree 3
.git/objects/70/d4408b5020e81d19906d6abdd87a73233ebf34 # commit 1
.git/objects/83/baae61804e65cc73a7201a7252750c76066a30 # test.txt v1
.git/objects/ca/c0cab538b970a37ea1e769cbbde608743bc96d # commit 2
.git/objects/95/cce637b4e889eee8042515db402128bd62c0d2 # commit 3
.git/objects/d6/70460b4b4aece5915caf5c68d12f560a9fe3e4 # 'test content'
.git/objects/d8/329fc1cc938780ffdd9f94e0d364e0ea74f579 # tree 1
.git/objects/fa/49b077972391ad58037050f2a75f74e3671e92 # new.txt
.git/objects/fd/f4fc3344e67ab068f836878b6c4951e3b15f3d # commit 1
----

If you follow all the internal pointers, you get an object graph something like this:
Expand Down
28 changes: 14 additions & 14 deletions book/10-git-internals/sections/refs.asc
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
[[_git_refs]]
=== Git References

If you were interested in seeing the history of your repository reachable from commit, say, `1a410e`, you could run something like `git log 1a410e` to display that history, but you would still have to remember that `1a410e` is the commit you want to use as the starting point for that history.
If you were interested in seeing the history of your repository reachable from commit, say, `95cce6`, you could run something like `git log 95cce6` to display that history, but you would still have to remember that `95cce6` is the commit you want to use as the starting point for that history.
Instead, it would be easier if you had a file in which you could store that SHA-1 value under a simple name so you could use that simple name rather than the raw SHA-1 value.

In Git, these simple names are called ``references'' or ``refs''; you can find the files that contain those SHA-1 values in the `.git/refs` directory.
Expand All @@ -20,41 +20,41 @@ To create a new reference that will help you remember where your latest commit i

[source,console]
----
$ echo 1a410efbd13591db07496601ebc7a059dd55cfe9 > .git/refs/heads/master
$ echo 95cce637b4e889eee8042515db402128bd62c0d2 > .git/refs/heads/master
----

Now, you can use the head reference you just created instead of the SHA-1 value in your Git commands:

[source,console]
----
$ git log --pretty=oneline master
1a410efbd13591db07496601ebc7a059dd55cfe9 Third commit
cac0cab538b970a37ea1e769cbbde608743bc96d Second commit
fdf4fc3344e67ab068f836878b6c4951e3b15f3d First commit
95cce637b4e889eee8042515db402128bd62c0d2 Third commit
1513b13a72f5277252cfce4ed0eda0620aca2f6a Second commit
70d4408b5020e81d19906d6abdd87a73233ebf34 First commit
----

You aren't encouraged to directly edit the reference files; instead, Git provides the safer command `git update-ref` to do this if you want to update a reference:

[source,console]
----
$ git update-ref refs/heads/master 1a410efbd13591db07496601ebc7a059dd55cfe9
$ git update-ref refs/heads/master 95cce637b4e889eee8042515db402128bd62c0d2
----

That's basically what a branch in Git is: a simple pointer or reference to the head of a line of work.
To create a branch back at the second commit, you can do this:

[source,console]
----
$ git update-ref refs/heads/test cac0ca
$ git update-ref refs/heads/test 1513b1
----

Your branch will contain only work from that commit down:

[source,console]
----
$ git log --pretty=oneline test
cac0cab538b970a37ea1e769cbbde608743bc96d Second commit
fdf4fc3344e67ab068f836878b6c4951e3b15f3d First commit
1513b13a72f5277252cfce4ed0eda0620aca2f6a Second commit
70d4408b5020e81d19906d6abdd87a73233ebf34 First commit
----

Now, your Git database conceptually looks something like this:
Expand Down Expand Up @@ -142,23 +142,23 @@ You can see this by creating an annotated tag (using the `-a` option):

[source,console]
----
$ git tag -a v1.1 1a410efbd13591db07496601ebc7a059dd55cfe9 -m 'Test tag'
$ git tag -a v1.1 95cce637b4e889eee8042515db402128bd62c0d2 -m 'Test tag'
----

Here's the object SHA-1 value it created:

[source,console]
----
$ cat .git/refs/tags/v1.1
9585191f37f7b0fb9444f35a9bf50de191beadc2
9585191f37f7b0fb9444f35a9bf50de191beadc2 -- TODO this hash
----

Now, run `git cat-file -p` on that SHA-1 value:

[source,console]
----
$ git cat-file -p 9585191f37f7b0fb9444f35a9bf50de191beadc2
object 1a410efbd13591db07496601ebc7a059dd55cfe9
$ git cat-file -p 9585191f37f7b0fb9444f35a9bf50de191beadc2 -- TODO this hash
object 95cce637b4e889eee8042515db402128bd62c0d2
type commit
tag v1.1
tagger Scott Chacon <[email protected]> Sat May 23 16:48:58 2009 -0700
Expand Down Expand Up @@ -201,7 +201,7 @@ Then, you can see what the `master` branch on the `origin` remote was the last t
[source,console]
----
$ cat .git/refs/remotes/origin/master
ca82a6dff817ec66f44342007202690a93763949
ca82a6dff817ec66f44342007202690a93763949 -- TODO can this have changed?
----

Remote references differ from branches (`refs/heads` references) mainly in that they're considered read-only.
Expand Down