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Éibhear Ó hAnluain 2022-09-23 20:33:41 +01:00
parent 5022169c08
commit d8288cef57
Signed by: eibhear
GPG key ID: D124FE9CF2177106
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@ -86,8 +86,9 @@
- Submarining :: the structure of a commit, "Content Addressable Filesystem", git objects - Submarining :: the structure of a commit, "Content Addressable Filesystem", git objects
- Unmanned submersibles :: the reflog, =fsck= and =gc=, finding and dealing with specific git objects - Unmanned submersibles :: the reflog, =fsck= and =gc=, finding and dealing with specific git objects
** About Éibhear Ó hAnluain ** About Éibhear Ó hAnluain
- Solutions Architect - Enterprise and Solutions Architect
+ eibhear.geo@gmail.com + e-mail: [[mailto:eibhear.geo@gmail.com][eibhear.geo@gmail.com]]
+ [matrix]: [[https://matrix.to/#/@eibhear:matrix.gibiris.org][@eibhear:matrix.gibiris.org]], [[https://matrix.to/#/@eibhear:matrix.org][@eibhear:matrix.org]]
- Software engineer since 1994 - Software engineer since 1994
- Using revision control since 1994: _subversion_, _git_, - Using revision control since 1994: _subversion_, _git_,
_IBM/Rational/Atria ClearCase_, _RCS_, _VSS_, _CVS_, _Serena _IBM/Rational/Atria ClearCase_, _RCS_, _VSS_, _CVS_, _Serena
@ -107,7 +108,8 @@
git config --local --list git config --local --list
git config --global --list git config --global --list
git config --system --list git config --system --list
git config [--system|--global|--local] <key> <value> git config [--system|--global|--local] <key> \
<value>
git config -e git config -e
#+END_SRC #+END_SRC
** =fetch= and =merge=, not =pull= ** =fetch= and =merge=, not =pull=
@ -196,315 +198,275 @@
#+REVEAL_HTML: </div> #+REVEAL_HTML: </div>
#+REVEAL_HTML: </div> #+REVEAL_HTML: </div>
** Merging appraoches: Decision tree ** Merging approaches: Decision tree
file:./images/merge-decision-tree-chart.png file:./images/merge-decision-tree-chart.png
* The Shallows * The Shallows
** Let's go a little deeper
*** A little deeper :B_block:BMCOL:
:PROPERTIES:
:BEAMER_col: 0.9
:BEAMER_env: block
:END:
file:./images/Naufragio_por_Gustavo_Gerdel.jpg
#+latex: {\tiny #+CAPTION: By Ggerdel - Foto de: Gustavo Gerdel (BAB Buceo) [[https://creativecommons.org/licenses/by-sa/4.0][CC BY-SA 4.0]], via Wikimedia Commons
By Ggerdel - Foto de: Gustavo Gerdel (BAB Buceo) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons #+ATTR_HTML: :width 70%
#+latex: } file:./images/Naufragio_por_Gustavo_Gerdel.jpg
** Refs ** Refs -- branches
*** Refs #+BEGIN_SRC shell
- Branches $ ls -1 .git/refs/heads/*
#+BEGIN_SRC .git/refs/heads/gitlab_10.x_upgrade
$ ls -1 .git/refs/heads/* .git/refs/heads/gitlab-ce-8.17
.git/refs/heads/gitlab_10.x_upgrade .git/refs/heads/gitlab-ce-9.1.4-defectFix
.git/refs/heads/gitlab-ce-8.17 .git/refs/heads/master
.git/refs/heads/gitlab-ce-9.1.4-defectFix
.git/refs/heads/master
$ cat .git/refs/heads/gitlab-ce-8.17 $ cat .git/refs/heads/gitlab-ce-8.17
c63767d0b9b520f36a533237624dfaa1256b463c c63767d0b9b520f36a533237624dfaa1256b463c
#+END_SRC #+END_SRC
** Refs ** Refs -- tags
*** Refs - tags
- tags #+BEGIN_SRC shell
#+BEGIN_SRC $ ls -1 .git/refs/tags/
$ ls -1 .git/refs/tags/ gitlab-cookbook-for-10.7.3
gitlab-cookbook-for-10.7.3 gitlab-cookbook-initial
gitlab-cookbook-initial gitlab-cookbook-rebaseline
gitlab-cookbook-rebaseline
$ cat .git/refs/tags/gitlab-cookbook-for-10.7.3 $ cat .git/refs/tags/gitlab-cookbook-for-10.7.3
f16b12027cef7052e09f3a483ace55999800ea5b f16b12027cef7052e09f3a483ace55999800ea5b
#+END_SRC #+END_SRC
- =HEAD= - =HEAD=
#+BEGIN_SRC #+BEGIN_SRC shell
$ cat .git/HEAD $ cat .git/HEAD
ref: refs/heads/gitlab_10.x_upgrade ref: refs/heads/gitlab_10.x_upgrade
#+END_SRC #+END_SRC
** Refs ** Refs -- remotes
*** Refs #+BEGIN_SRC shell
- remotes $ ls -1 .git/refs/remotes/origin/*
#+BEGIN_SRC .git/refs/remotes/origin/ara_test
$ ls -1 .git/refs/remotes/origin/* .git/refs/remotes/origin/brjones_aci_network
.git/refs/remotes/origin/ara_test .git/refs/remotes/origin/gitlab_10.x_upgrade
.git/refs/remotes/origin/brjones_aci_network .git/refs/remotes/origin/gitlab-ce-8.17
.git/refs/remotes/origin/gitlab_10.x_upgrade .git/refs/remotes/origin/gitlab-ce-9.1.4-defectFix
.git/refs/remotes/origin/gitlab-ce-8.17 .git/refs/remotes/origin/HEAD
.git/refs/remotes/origin/gitlab-ce-9.1.4-defectFix .git/refs/remotes/origin/master
.git/refs/remotes/origin/HEAD
.git/refs/remotes/origin/master
$ cat .git/refs/remotes/origin/ara_test $ cat .git/refs/remotes/origin/ara_test
7130b7ee374ad9f7ba784ec0b0d0b86dc99f41d4 7130b7ee374ad9f7ba784ec0b0d0b86dc99f41d4
#+END_SRC #+END_SRC
** HEAD ** HEAD
*** HEAD - =HEAD= is a ref that points to where the commit currently checked out
- =HEAD= is a ref that points to where the commit currently checked out - =HEAD= in a remote repository usually points to the default branch
- =HEAD= in a remote repository usually points to the default branch
#+BEGIN_SRC #+BEGIN_SRC shell
$ cat .git/HEAD $ cat .git/HEAD
ref: refs/heads/master ref: refs/heads/master
$ cat .git/refs/remotes/origin/HEAD $ cat .git/refs/remotes/origin/HEAD
ref: refs/remotes/origin/REL2_0 ref: refs/remotes/origin/REL2_0
#+END_SRC #+END_SRC
** Annotated tags ** Annotated tags 1/2
*** Annotated tags - A normal tag is just a "ref", pointing to a commit.
- A normal tag is just a "ref", pointing to a commit. #+BEGIN_SRC shell
#+BEGIN_SRC shell git tag Rel1.0 Rel1
git tag Rel1.0 Rel1 cat .git/refs/tags/Rel1.0
cat .git/refs/tags/Rel1.0 git cat-file -t $(cat .git/refs/tags/Rel1.0)
git cat-file -t $(cat .git/refs/tags/Rel1.0) git cat-file -p $(cat .git/refs/tags/Rel1.0)
git cat-file -p $(cat .git/refs/tags/Rel1.0) #+END_SRC
#+END_SRC - Caveat :: tags and branches use different namespaces, so
- *Caveat*: tags and branches use different namespaces, so temptation to tag the =Rel1= branch with =Rel1= would be
temptation to tag the =Rel1= branch with =Rel1= would be high. However, this causes confusion for many git tools, so
high. However, this causes confusion for many git tools, so should be avoided.
should be avoided. ** Annotated tags 2/2
** Annotated tags - An annotated tag is a separate git object, that records
*** Annotated tags information specfic to the tag:
- An annotated tag is a separate git object, that records information specfic to the tag: + Tag name; date; tagger; commit it's pointing to
+ Tag name; date; tagger; commit it's pointing to - Advice is for annotated tags to be used for significant
- Advice is for annotated tags to be used for significant announcements/releases/snaphots. announcements/releases/snaphots.
#+BEGIN_SRC shell #+BEGIN_SRC shell
git tag -a -m "Formal release of 1.0" \ git tag -a -m "Formal release of 1.0" Rel1.0.prod Rel1
Rel1.0.prod Rel1 cat .git/refs/tags/Rel1.0.prod
cat .git/refs/tags/Rel1.0.prod git cat-file -t $(cat .git/refs/tags/Rel1.0.prod)
git cat-file -t $(cat .git/refs/tags/Rel1.0.prod) git cat-file -p $(cat .git/refs/tags/Rel1.0.prod)
git cat-file -p $(cat .git/refs/tags/Rel1.0.prod) #+END_SRC
#+END_SRC
** blame ** blame
*** =blame= - Identifies the commit, commit author and date for each line in a
- Identifies the commit, commit author and date for each line in a file. file.
- Doesn't give information for lines that have been removed or replaced. - Doesn't give information for lines that have been removed or
replaced.
** Tag and commit signing ** Tag and commit signing
*** Tag and commit signing and verification - PGP/GnuPG (=gpg=): expects familiarity with public/private key encryption.
- PGP/GnuPG (=gpg=): expects familiarity with public/private key encryption. - Sign tags and commits with private key to assure integrity
- Sign tags and commits with private key to assure integrity #+BEGIN_SRC shell
#+BEGIN_SRC shell git commit -Seibhear.geo@gmail.com -m \
git commit -Seibhear.geo@gmail.com \ "Update to information.md"
-m "Update to information.md" git cat-file -p $(cat .git/refs/heads/master)
git cat-file -p $(cat .git/refs/heads/master) git tag -s -u eibhear.geo@gmail.com -m "Release 2." Rel2.0 \
git tag -s -u eibhear.geo@gmail.com \ Rel2
-m "Release 2." Rel2.0 Rel2 git cat-file -p $(cat .git/refs/tags/Rel2.0)
git cat-file -p $(cat .git/refs/tags/Rel2.0) #+END_SRC
#+END_SRC - Verify commits and tags with public key
- Verify commits and tags with public key #+BEGIN_SRC shell
#+BEGIN_SRC git tag -v Rel2.0
git tag -v Rel2.0 git log --show-signature -1
git log --show-signature -1 #+END_SRC
#+END_SRC
* The Continental shelf * The Continental shelf
**
*** Switch on the Sonar :B_block:BMCOL:
:PROPERTIES:
:BEAMER_col: 0.9
:BEAMER_env: block
:END:
file:./images/Loligo_vulgaris.jpg
#+latex: {\tiny #+CAPTION: By © Hans Hillewaert, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=385705
By © Hans Hillewaert, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=385705 #+ATTR_HTML: :width 70%
#+latex: } file:./images/Loligo_vulgaris.jpg
** Git Objects -- blobs ** Git Objects -- blobs
*** Blob (file) - A file
A file #+BEGIN_SRC shell
#+BEGIN_SRC shell $ cat ~/.profile | git hash-object \
$ cat ~/.profile | git hash-object --stdin --stdin
c9db4591825bd7a918df686ff04aeb3a87d3bda0 c9db4591825bd7a918df686ff04aeb3a87d3bda0
#+END_SRC #+END_SRC
** Git Objects -- trees ** Git Objects -- trees
*** Tree - A listing of files and other tree objects containing the
A listing of files and other tree objects containing the following information on each: access mode (similar to UNIX
following information on each: access mode (similar to UNIX permissions); type (e.g. =tree=, =blob=); SHA1; file/directory
permissions); type (e.g. =tree=, =blob=); SHA1; file/directory name
name #+BEGIN_SRC shell
#+BEGIN_SRC shell $ git cat-file -p 2c4e4782bcb6b13a0e11b6961004dec8745e9d35
$ git cat-file -p \ 040000 tree bcd2824258ddf007dae7f88da7d727fb3894691b Astro
2c4e4782bcb6b13a0e11b6961004dec8745e9d35 100644 blob 94aea57573b92d9188a3df4cf748b60efd968803 MyHelloWorldBean.java
040000 tree bcd2824258ddf007dae7f88da7d727fb3894691b 100644 blob c55118d1afb2be6a6d0f728814c084d54e97db14 MyHelloWorldServlet.java
Astro #+END_SRC
100644 blob 94aea57573b92d9188a3df4cf748b60efd968803 ** Git Objects -- commits 1/2
MyHelloWorldBean.java Information on a commit event:
100644 blob c55118d1afb2be6a6d0f728814c084d54e97db14 - The SHA1 of the top-level tree of the project.
MyHelloWorldServlet.java - The parent commit (or commits, if this commit is the result of a
#+END_SRC merge)
** Git Objects -- commits - The details of the author of the code that is being applied with
*** Commit the commit (including date and time)
Information on a commit event: - The details of the person who applied the commit (including date and time)
- The SHA1 of the top-level tree of the project. - The commit gpg signature, if present
- The parent commit (or commits, if this commit is the result of - The commit comment
a merge) ** Git Objects -- commits 2/2
- The details of the author of the code that is being applied #+BEGIN_SRC shell
with the commit (including date and time) $ git cat-file -p 37c5611a177c9eafbd17e4302b6d644434b1042b
- The details of the person who applied the commit (including date and time) tree 40b6262f3f3f5fc8cb8a0c78ca558a683dfc2323
- The commit gpg signature, if present parent 42608808a973b8e0c4a4b0105c2317d81b12851f
- The commit comment parent 36d56f097ca81f06d77f46cbde3fc10cbf6639f9
** Git Objects -- commits author Master O'Theuniverse <master.otheuniverse@example.com> 1529840879 +0100
*** Commit committer Master O'Theuniverse <master.otheuniverse@example.com> 1529840879 +0100
#+BEGIN_SRC shell
$ git cat-file -p \
37c5611a177c9eafbd17e4302b6d644434b1042b
tree 40b6262f3f3f5fc8cb8a0c78ca558a683dfc2323
parent 42608808a973b8e0c4a4b0105c2317d81b12851f
parent 36d56f097ca81f06d77f46cbde3fc10cbf6639f9
author Master O'Theuniverse \
<master.otheuniverse@example.com> \
1529840879 +0100
committer Master O'Theuniverse \
<master.otheuniverse@example.com> \
1529840879 +0100
REV18_5 now live REV18_5 now live
#+END_SRC #+END_SRC
** Git Objects -- tags ** Git Objects -- tags 1/2
*** Tag A tag points to a commit object, and an annotated tag contains
A tag points to a commit object, and an annotated tag contains additional information
additional information - What object it's pointing at and its type
- What object it's pointing at and its type - The name of the tag
- The name of the tag - Who applied the tag (including date and time)
- Who applied the tag (including date and time) - A tag comment
- A tag comment ** Git Objects -- tags 2/2
** Git Objects -- tags #+BEGIN_SRC shell
*** Tag $ git cat-file -p 88a4c18867ccb1d7c398f285460d8abab3964e75
#+BEGIN_SRC shell object 66d8336c2770d0d1cea3dcb0175611edb5e69f69
$ git cat-file -p \ type commit
88a4c18867ccb1d7c398f285460d8abab3964e75 tag Rel1.0.a
object 66d8336c2770d0d1cea3dcb0175611edb5e69f69 tagger Éibhear Ó hAnluain <eibhear.geo@gmail.com> 1529847749 +0100
type commit
tag Rel1.0.a
tagger Éibhear Ó hAnluain \
<eibhear.geo@gmail.com> \
1529847749 +0100
An annotated tag for the Rel1 release An annotated tag for the Rel1 release
$ git cat-file -t \ $ git cat-file -t 66d8336c2770d0d1cea3dcb0175611edb5e69f69
66d8336c2770d0d1cea3dcb0175611edb5e69f69 commit
commit #+END_SRC
#+END_SRC
** "Content Addressable Filesystem" ** "Content Addressable Filesystem"
*** "Content Addressable Filesystem"
As the IDs of objects are based on their contents, they are As the IDs of objects are based on their contents, they are
located in the git database according to that name located in the git database according to that name
#+BEGIN_SRC shell #+BEGIN_SRC shell
git rev-list --all --objects git rev-list --all --objects
git cat-file -p \ git cat-file -p b5aea839bc89a0c7931af469ff9c145be18854d7
b5aea839bc89a0c7931af469ff9c145be18854d7 git cat-file -p b5aea839bc89a0c7931af469ff9c145be18854d7 | \
git cat-file -p \
b5aea839bc89a0c7931af469ff9c145be18854d7 | \
git hash-object --stdin git hash-object --stdin
ls -l .git/objects/b5/aea839bc89a0c7931af469ff9c145be18854d7 ls -l .git/objects/b5/aea839bc89a0c7931af469ff9c145be18854d7
#+END_SRC #+END_SRC
* The Deep trenches * The Deep trenches -- Exotic creatures
**
*** Exotic creatures :B_block:BMCOL:
:PROPERTIES:
:BEAMER_col: 0.7
:BEAMER_env: block
:END:
file:./images/Alvinella_pompejana01.jpg
#+latex: {\tiny #+CAPTION: By National Science Foundation (University of Delaware College of Marine Studies) - http://www.nsf.gov/od/lpa/news/press/01/pr0190.htm, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7123122
By National Science Foundation (University of Delaware College of Marine Studies) - http://www.nsf.gov/od/lpa/news/press/01/pr0190.htm, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7123122 #+ATTR_HTML: :width 60%
#+latex: } file:./images/Alvinella_pompejana01.jpg
** The reflog ** The reflog
*** The reflog - A log of all the changes to HEAD
- A log of all the changes to HEAD - Local only: not involved in pulls, pushes or fetches.
- Local only: not involved in pulls, pushes or fetches. - Useful for recovering accidentally removed commits
- Useful for recovering accidentally removed commits - Completely clear the reflog
- Completely clear the reflog #+BEGIN_SRC shell
: git reflog expire --expire=now \ git reflog expire --expire=now --expire-unreachable=now \
: --expire-unreachable=now --verbose --all --verbose --all
#+END_SRC
** fsck and gc ** fsck and gc
*** fsck and gc - fsck :: Analyse connectivity of the objects in the git
- fsck :: Analyse connectivity of the objects in the git database. Useful for finding objects that aren't of any use any
database. Useful for finding objects that aren't of any more.
use any more. - gc :: "Garbage collector". Compress and pack objects, remove
- gc :: "Garbage collector". Compress and pack objects, remove "danlging" and unreachable objects
"danlging" and unreachable objects
** Useful commands ** Useful commands
*** Useful commands - Find the largest object in your git database
- Find the largest object in your git database #+BEGIN_SRC shell
#+BEGIN_SRC shell git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize)' \
git cat-file \ --batch-all-objects | sed -n 's/^blob //p' | sort -n --key=2
--batch-check='%(objecttype) %(objectname) %(objectsize)' \ #+END_SRC
--batch-all-objects | sed -n 's/^blob //p' | \ - List all objects in your git database
sort -n --key=2 #+BEGIN_SRC shell
#+END_SRC git rev-list --all --objects
- List all objects in your git database #+END_SRC
: git rev-list --all --objects - Determine the filename related to a blob object
- Determine the filename related to a blob object #+BEGIN_SRC shell
: git rev-list --objects --all | grep <objectID> git rev-list --objects --all | grep <objectID>
- Determine commits that reference that file #+END_SRC
: git log --follow -- "<fileNameAndPath>" - Determine commits that reference that file
** Permanently removing a file from your git db #+BEGIN_SRC shell
*** Permanently removing a file from your git db git log --follow -- "<fileNameAndPath>"
- e.g. contains password information, v. large file not required, etc. #+END_SRC
- For each branch... ** Permanently removing a file from your git db 1/2
+ Check it out - e.g. contains password information, v. large file not required, etc.
: git checkout <branch> - For each branch...
+ Remove the file from all commits + Check it out
#+BEGIN_SRC shell #+BEGIN_SRC shell
git filter-branch --tree-filter \ git checkout <branch>
'rm -f <filePathAndName>' \ #+END_SRC
--prune-empty HEAD + Remove the file from all commits
#+END_SRC #+BEGIN_SRC shell
+ Clean up the original refs git filter-branch --tree-filter \
#+BEGIN_SRC shell 'rm -f <filePathAndName>' --prune-empty HEAD
git for-each-ref --format="%(refname)" \ #+END_SRC
refs/original/ | \ + Clean up the original refs
xargs -n 1 git update-ref -d #+BEGIN_SRC shell
#+END_SRC git for-each-ref --format="%(refname)" refs/original/ | \
** Permanently removing a file from your git db xargs -n 1 git update-ref -d
*** Permanently removing a file from your git db #+END_SRC
- ... then ... ** Permanently removing a file from your git db 2/2
- Clear out the reflog - ... then ...
: git reflog expire --expire-unreachable=now --all - Clear out the reflog
The reflog maintains references to commits and objects you #+BEGIN_SRC shell
may want to remove. git reflog expire --expire-unreachable=now --all
- Collect the garbage, regardless of age #+END_SRC
: git gc --prune=now The reflog maintains references to commits and objects you may
- Sanity-check all objects want to remove.
: git fsck --unreachable --no-reflogs - Collect the garbage, regardless of age
#+BEGIN_SRC shell
git gc --prune=now
#+END_SRC
- Sanity-check all objects
#+BEGIN_SRC shell
git fsck --unreachable --no-reflogs
#+END_SRC
** Other interesting concepts ** Other interesting concepts
*** Other interesting concepts - Porcelain vs Plumbing :: The commands that we use vs the
- *Porcelain vs Plumbing*: The commands that we use vs the commands that *they* use. commands that *they* use.
+ *Porcelain*: =init=, =clone=, =fetch=, =push=, =add=, =commit=, etc. + Porcelain :: =init=, =clone=, =fetch=, =push=, =add=,
+ *Plumbing*: =hash-object=, =cat-file=, =write-tree=, =count-objects=, etc. =commit=, etc.
- *submodules*: to link a separate git repository into yours + Plumbing :: =hash-object=, =cat-file=, =write-tree=,
- *fast-import*: to import data into a git repository from other, =count-objects=, etc.
non-git sources (e.g. cvs, subversion, etc.) - submodules :: to link a separate git repository into yours
- fast-import :: to import data into a git repository from other,
non-git sources (e.g. cvs, subversion, etc.)
** Resources ** Resources
*** Resources - The git book :: https://git-scm.com/book/en/v2/
- The git book :: https://git-scm.com/book/en/v2/ - The git manual ::
- The git manual :: #+BEGIN_SRC shell
#+BEGIN_SRC shell git help --all
git help --all git help merge
git help merge git help cat-file
git help cat-file man git-hash-object
man git-hash-object #+END_SRC
#+END_SRC - Stack overflow :: https://stackoverflow.com/questions/tagged/git
- Stack overflow :: https://stackoverflow.com/questions/tagged/git
* Commands :noexport: * Commands :noexport:
| | add | | | add |
| | add--interactive | | | add--interactive |

5
styles/e-reveal.css
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@ -16,7 +16,6 @@ section {
pre, pre,
code { code {
font-size: 80%;
color: #000000; color: #000000;
background-color: #e0e0e0; background-color: #e0e0e0;
border-style: solid; border-style: solid;
@ -24,11 +23,13 @@ code {
border-color: #c0c0c0; border-color: #c0c0c0;
} }
pre { .org-src-container > pre {
padding: 0.5em; padding: 0.5em;
font-size: 100%;
} }
code { code {
font-size: 80%;
padding-right: 1px; padding-right: 1px;
padding-left: 1px; padding-left: 1px;
} }