Write initial patchfiles documentation

[tsimonq2]

A few gems in here, plus the relevant links to Debian Policy. Feel free to make minor modifications before merging if needed.

[eeickmeyer]

Just of note, if someone wants to make it easy on themselves:

git-cola is really useful when creating patchfiles in this case. One can simply make a branch or otherwise mock a git commit then go to "View DAG" which brings up the graph, then right-click on the commit, and click on "Create Patch" which will then create a DEP-3 formatted patch in a "Patches" directory in the root of the git repo beginning with "0001-". Makes it then easy to add to debian/patches and put into the proper sequence to add to series.

The more you know! 🌈 ⭐

[dviererbe]

Just of note, if someone wants to make it easy on themselves:

git-cola is really useful when creating patchfiles in this case. One can simply make a branch or otherwise mock a git commit then go to "View DAG" which brings up the graph, then right-click on the commit, and click on "Create Patch" which will then create a DEP-3 formatted patch in a "Patches" directory in the root of the git repo beginning with "0001-". Makes it then easy to add to debian/patches and put into the proper sequence to add to series.

The more you know! 🌈 ⭐

praise: Good to know, this a really nice tool :)
note: I think this does not fit into the topic of managing patch files.
thought: But we could create a reference article with a list of tools (relevant to the packaging topic) that exists.

[dviererbe]

note: I merged my work on documenting patch management into this PR branch.

I moved a lot of the work by @tsimonq2 into an explanation article, which is linked at the top of the how-to.

todo: @rkratky This PR is ready for review by you.

[dviererbe]

issue: There are SRU docs in the diff???

[dviererbe]

issue: There are SRU docs in the diff???

Solved it:

• I rebased how-to/patch-management branch onto preview/2.0
• I rebased tsimonq2 branch onto preview/2.0
• then I merged them

[dviererbe]

note: the linkcheck failures can be ignored

(reference/architectures: line   66) broken    https://canonical.com/blog/statement-on-32-bit-i386-packages-for-ubuntu-19-10-and-20-04-lts - 500 Server Error:  for url: https://canonical.com/blog/statement-on-32-bit-i386-packages-for-ubuntu-19-10-and-20-04-lts
(reference/glossary: line  681) broken    https://www.gnu.org - HTTPSConnectionPool(host='www.gnu.org', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f2f96b8a140>: Failed to establish a new connection: [Errno 101] Network is unreachable'))
(explanation/package-model: line   80) broken    https://www.gnu.org/software/bash/ - HTTPSConnectionPool(host='www.gnu.org', port=443): Max retries exceeded with url: /software/bash/ (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f2f969e2470>: Failed to establish a new connection: [Errno 101] Network is unreachable'))

The links all work

[dviererbe]

note: This how-to does not show how to easily generate a patchfile with git-ubuntu. I created this task as #94 – marked as a good first issue.

[dviererbe]

praise: thanks for catching the typo