6 files changed, 307 insertions, 0 deletions
diff --git a/src/content/en/tils/2020/11/08/find-broken-symlink.adoc b/src/content/en/tils/2020/11/08/find-broken-symlink.adoc
new file mode 100644
index 0000000..624d24a
--- /dev/null
+++ b/src/content/en/tils/2020/11/08/find-broken-symlink.adoc
@@ -0,0 +1,25 @@
+= Find broken symlinks with "find"
+:categories: shell
+
+:annex:        https://git-annex.branchable.com/
+:annex-wanted: https://git-annex.branchable.com/git-annex-wanted/
+
+The `find` command knows how to show broken symlinks:
+
+[source,sh]
+----
+find . -xtype l
+----
+
+This was useful to me when combined with {annex}[Git Annex].  Its
+{annex-wanted}[`wanted`] option allows you to have a "sparse" checkout of the
+content, and save space by not having to copy every annexed file locally:
+
+[source,sh]
+----
+git annex wanted . 'exclude=Music/* and exclude=Videos/*'
+----
+
+You can `find` any broken symlinks outside those directories by querying with
+Git Annex itself, but `find . -xtype l` works on other places too, where broken
+symlinks might be a problem.
diff --git a/src/content/en/tils/2020/11/12/diy-nix-bash-ci.adoc b/src/content/en/tils/2020/11/12/diy-nix-bash-ci.adoc
new file mode 100644
index 0000000..97ace30
--- /dev/null
+++ b/src/content/en/tils/2020/11/12/diy-nix-bash-ci.adoc
@@ -0,0 +1,63 @@
+= DIY bare bones CI server with Bash and Nix
+:categories: ci
+:sort: 2
+
+:post-receive: https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks
+:example-project: https://euandreh.xyz/remembering/ci.html
+
+With a server with Nix installed (no need for NixOS), you can leverage its build
+isolation for running CI jobs by adding a {post-receive}[post-receive] Git hook
+to the server.
+
+In most of my project I like to keep a `test` attribute which runs the test with
+`nix-build -A test`.  This way, a post-receive hook could look like:
+
+[source,sh]
+----
+#!/usr/bin/env bash
+set -Eeuo pipefail
+set -x
+
+LOGS_DIR="/data/static/ci-logs/libedn"
+mkdir -p "$LOGS_DIR"
+LOGFILE="${LOGS_DIR}/$(date -Is)-$(git rev-parse master).log"
+exec &> >(tee -a "${LOGFILE}")
+
+unset GIT_DIR
+CLONE="$(mktemp -d)"
+git clone . "$CLONE"
+pushd "$CLONE"
+
+finish() {
+  printf "\n\n>>> exit status was %s\n" "$?"
+}
+trap finish EXIT
+
+nix-build -A test
+----
+
+We initially (lines #5 to #8) create a log file, named after _when_ the run is
+running and for _which_ commit it is running for.  The `exec` and `tee` combo
+allows the output of the script to go both to `stdout` _and_ the log file.  This
+makes the logs output show up when you do a `git push`.
+
+Lines #10 to #13 create a fresh clone of the repository and line #20 runs the
+test command.
+
+After using a similar post-receive hook for a while, I now even generate a
+simple HTML file to make the logs available ({example-project}[example project])
+through the browser.
+
+== Upsides
+
+No vendor lock-in, as all you need is a server with Nix installed.
+
+And if you pin the Nixpkgs version you're using, this very simple setup yields
+extremely sandboxed runs on a very hermetic environment.
+
+== Downsides
+
+Besides the many missing shiny features of this very simplistic CI, `nix-build`
+can be very resource intensive.  Specifically, it consumes too much memory.  So
+if it has to download too many things, or the build closure gets too big, the
+server might very well run out of memory.
diff --git a/src/content/en/tils/2020/11/12/git-bisect-automation.adoc b/src/content/en/tils/2020/11/12/git-bisect-automation.adoc
new file mode 100644
index 0000000..dff8737
--- /dev/null
+++ b/src/content/en/tils/2020/11/12/git-bisect-automation.adoc
@@ -0,0 +1,25 @@
+= Git bisect automation
+:categories: git
+:sort: 1
+
+It is good to have an standardized way to run builds and tests on the repository
+of a project, so that you can find when a bug was introduced by using
+`git bisect run`.
+
+I've already been in the situation when a bug was introduced and I didn't know
+how it even was occurring, and running Git bisect over hundreds of commits to
+pinpoint the failing commit was very empowering:
+
+[source,sh]
+----
+$ GOOD_COMMIT_SHA=e1fd0a817d192c5a5df72dd7422e36558fa78e46
+$ git bisect start HEAD $GOOD_COMMIT_SHA
+$ git bisect run sn -c './build.sh && ./run-failing-case.sh'
+----
+
+Git will than do a binary search between the commits, and run the commands you
+provide it with to find the failing commit.
+
+Instead of being afraid of doing a bisect, you should instead leverage it, and
+make Git help you dig through the history of the repository to find the bad
+code.
diff --git a/src/content/en/tils/2020/11/12/useful-bashvars.adoc b/src/content/en/tils/2020/11/12/useful-bashvars.adoc
new file mode 100644
index 0000000..fb148fb
--- /dev/null
+++ b/src/content/en/tils/2020/11/12/useful-bashvars.adoc
@@ -0,0 +1,61 @@
+= Useful Bash variables
+:categories: shell
+
+:bash:                   https://www.gnu.org/software/bash/
+:bash-bang-bang:         https://www.gnu.org/software/bash/manual/bash.html#Event-Designators
+:bash-dollar-underscore: https://www.gnu.org/software/bash/manual/bash.html#Special-Parameters
+
+{bash}[GNU Bash] has a few two letter variables that may be useful when typing
+on the terminal.
+
+== `!!`: the text of the last command
+
+The {bash-bang-bang}[`!!` variable] refers to the previous command, and I find
+useful when following chains for symlinks:
+
+[source,sh]
+----
+$ which git
+/run/current-system/sw/bin/git
+$ readlink $(!!)
+readlink $(which git)
+/nix/store/5bgr1xpm4m0r72h9049jbbhagxdyrnyb-git-2.28.0/bin/git
+----
+
+It is also useful when you forget to prefix `sudo` to a command that requires
+it:
+
+[source,sh]
+----
+$ requires-sudo.sh
+requires-sudo.sh: Permission denied
+$ sudo !!
+sudo ./requires-sudo.sh
+# all good
+----
+
+Bash prints the command expansion before executing it, so it is better for you
+to follow along what it is doing.
+
+== `$_`: most recent parameter
+
+The {bash-dollar-underscore}[`$_` variable] will give you the most recent
+parameter you provided to a previous argument, which can save you typing
+sometimes:
+
+[source,sh]
+----
+# instead of...
+$ mkdir -p a/b/c/d/
+$ cd a/b/c/d/
+
+# ...you can:
+$ mkdir -p a/b/c/d/
+$ cd $_
+----
+
+== Conclusion
+
+I wouldn't use those in a script, as it would make the script terser to read, I
+find those useful shortcut that are handy when writing at the interactive
+terminal.
diff --git a/src/content/en/tils/2020/11/14/gpodder-media.adoc b/src/content/en/tils/2020/11/14/gpodder-media.adoc
new file mode 100644
index 0000000..f722f35
--- /dev/null
+++ b/src/content/en/tils/2020/11/14/gpodder-media.adoc
@@ -0,0 +1,21 @@
+= gPodder as a media subscription manager
+
+:re-discover: https://www.charlieharrington.com/unexpected-useless-and-urgent
+:gpodder: https://gpodder.github.io/
+
+As we {re-discover}[re-discover] the value of Atom/RSS feeds, most useful feed
+clients I know of don't support media, specifically audio and video.
+
+{gpodder}[gPodder] does.
+
+It is mostly know as a desktop podcatcher.  But the thing about podcasts is that
+the feed is provided through an RSS/Atom feed.  So you can just use gPodder as
+your media feed client, where you have control of what you look at.
+
+I audio and video providers I know of offer an RSS/Atom view of their content,
+so you can, say, treat any YouTube channel like a feed on its own.
+
+gPodder will then managed your feeds, watched/unwatched, queue downloads, etc.
+
+Being obvious now, it was a big finding for me.  If it got you interested, I
+recommend you giving gPodder a try.
diff --git a/src/content/en/tils/2020/11/30/git-notes-ci.adoc b/src/content/en/tils/2020/11/30/git-notes-ci.adoc
new file mode 100644
index 0000000..48a996b
--- /dev/null
+++ b/src/content/en/tils/2020/11/30/git-notes-ci.adoc
@@ -0,0 +1,112 @@
+= Storing CI data on Git notes
+:categories: git ci
+
+:git-notes: https://git-scm.com/docs/git-notes
+:nix-bash-ci: link:../12/diy-nix-bash-ci.html
+:cgit: https://git.zx2c4.com/cgit/
+
+Extending the bare bones CI server I've {nix-bash-ci}[talked about before],
+divoplade on Freenode suggested storing CI artifacts on {git-notes}[Git notes],
+such as tarballs, binaries, logs, _etc_.
+
+I've written a small script that will put log files and CI job data on Git
+notes, and make it visible on the porcelain log.  It is a simple extension of
+the previous article:
+
+[source,sh]
+----
+#!/usr/bin/env bash
+set -Eeuo pipefail
+set -x
+
+PREFIX='/srv/ci/vps'
+mkdir -p "$PREFIX"
+read -r _ SHA _ # oldrev newrev refname
+FILENAME="$(date -Is)-$SHA.log"
+LOGFILE="$PREFIX/$FILENAME"
+exec &> >(tee -a "$LOGFILE")
+
+echo "Starting CI job at: $(date -Is)"
+
+finish() {
+  STATUS="$?"
+  printf "\n\n>>> exit status was %s\n" "$STATUS"
+  echo "Finishing CI job at: $(date -Is)"
+  popd
+  NOTE=$(cat <<EOF
+See CI logs with:
+  git notes --ref=refs/notes/ci-logs show $SHA
+  git notes --ref=refs/notes/ci-data show $SHA
+EOF
+)
+  git notes --ref=refs/notes/ci-data add -f -m "$STATUS $FILENAME"
+  git notes --ref=refs/notes/ci-logs add -f -F "$LOGFILE"
+  git notes add -f -m "$NOTE"
+  printf "\n\n>>> CI logs added as Git note."
+}
+trap finish EXIT
+
+unset GIT_DIR
+CLONE="$(mktemp -d)"
+git clone . "$CLONE"
+pushd "$CLONE"
+git config --global user.email git@euandre.org
+git config --global user.name 'EuAndreh CI'
+
+./container make check site
+./container make publish
+----
+
+The important part is in the `finish()` function: - #25 stores the exit status
+and the generated filename separated by spaces; - #26 adds the log file in a
+note using the `refs/notes/ci-logs` ref; - #27 it adds a note to the commit
+saying how to see the logs.
+
+A commit now has an attached note, and shows it whenever you look at it:
+
+[source,diff]
+----
+$ git show 87c57133abd8be5d7cc46afbf107f59b26066575
+commit 87c57133abd8be5d7cc46afbf107f59b26066575
+Author: EuAndreh <eu@euandre.org>
+Date:   Wed Feb 24 21:58:28 2021 -0300
+
+    vps/machines.scm: Change path to cronjob files
+
+Notes:
+    See CI logs with:
+      git notes --ref=refs/notes/ci-logs show 87c57133abd8be5d7cc46afbf107f59b26066575
+      git notes --ref=refs/notes/ci-data show 87c57133abd8be5d7cc46afbf107f59b26066575
+
+diff --git a/servers/vps/machines.scm b/servers/vps/machines.scm
+index d1830ca..a4ccde7 100644
+--- a/servers/vps/machines.scm
++++ b/servers/vps/machines.scm
+@@ -262,8 +262,8 @@ pki " mail-domain " key  \"" (tls-priv-for mail-domain) "\""))
+             (service mcron-service-type
+                      (mcron-configuration
+                       (jobs
+-                       (list #~(job "30 1 * * 1" "guix gc -d")
+-                             #~(job "30 0 * * *" "/var/lib/euandreh/backup.sh")))))
++                       (list #~(job "30 1 * * 1" "/opt/bin/gc.sh")
++                             #~(job "30 0 * * *" "/opt/bin/backup.sh")))))
+             (service dhcp-client-service-type)
+             #;
+             (service opensmtpd-service-type
+----
+
+Other tools such as {cgit}[cgit] will also show notes on the web interface:
+https://euandre.org/git/servers/commit?id=87c57133abd8be5d7cc46afbf107f59b26066575.
+
+You can go even further: since cgit can serve raw blob directly, you can even
+serve such artifacts (log files, release artifacts, binaries) from cgit itself:
+
+[source,sh]
+----
+$ SHA="$(git notes --ref=refs/notes/ci-logs list 87c57133abd8be5d7cc46afbf107f59b26066575)"
+$ echo "https://euandre.org/git/servers/blob?id=$SHA"
+https://euandre.org/git/servers/blob?id=1707a97bae24e3864fe7943f8dda6d01c294fb5c
+----
+
+And like that you'll have cgit serving the artifacts for you:
+https://euandre.org/git/servers/blob?id=1707a97bae24e3864fe7943f8dda6d01c294fb5c.