I am trying to work out a helper for creating more meaningful automated commit messages for reprostim where we collect videos and annex assistant moves them to the server.

<details>
<summary>I was about to file this TODO report describing more detail before I realized that in principle git has a hook I could use</summary> 

ATM (git annex 10.20231227-1~ndall+1) git annex assistant just commits with a generic non-descript (besides location) commit message e.g.

```
git-annex in reprostim@reproiner:/data/reprostim
```

and to figure out what actually git-annex has done takes at least rerunning `git log --stat` but in git gui of some kind takes looking at each and every commit to identify the one of interest (which e.g. modified `config.yaml`) or specific filtering etc.

I would have appreciated if commits became more descriptive. Since git-annex assistant is quite reactive and (at least in our case) mostly commits one file change at a time I would have appreciated commit messages like

```
Edited config.yaml
```

or `Addded` or `Removed`.  If file is under a folder and length of the path is over some limit, would have abbreviated path to smth like ```.../config.yaml```.

In case of multiple files per "action", summarized in numbers and possibly again with a hint on location

```
Edited config.yaml, added 10 files under Videos/
```

Moreover, I would have still appreciated that information annex reports about location now, but I would have made it into the extended part of the commit message after a new line, and added a version info.  So altogether could have looked like

```
Edited config.yaml, added 10 files under Videos/

---
# git annex metadata
repository: reprostim@reproiner:/data/reprostim
version: 10.20231227-1~ndall+1
```

And even more "ideally", if it could pick up (if exists) an optional file (e.g. `.git/ANNEX_COMMIT_META.yaml`) or some `git config` field to add to the commit, I could have then added information about the system/software I care about, e.g.

```
reprostim-version: 0.20240202.0
```

and thus have commit carrying metadata about the version which produces those video files.  ATM the video capture is completely ignorant of git-annex so I cannot go and metadata annotate those files... but that would be a different issue ... ;)

As some kind of testament to possibility and usability of such commits, could navigate through commits of our automated datalad dandisets e.g. [000108](https://github.com/dandisets/000108/commits/draft/) where now without any extra tools etc I can tell where we added or removed files or just modified some metadata. It is indeed custom and more specific to our use case, but I think aforementioned would already be better.

</details>

<details>
<summary>But when I created this experimental version of the script to see what info I have available</summary> 

```shell
#!/bin/sh
#
# A hook to provide custom commit messages for
# changes in the repo which would be better than default ones git-annex provides.

COMMIT_MSG_FILE=$1
COMMIT_SOURCE=$2
SHA1=$3

if [ -n "$COMMIT_MSG_FILE" ]; then
	orig_msg=$(cat "$COMMIT_MSG_FILE")
else
	orig_msg=NONE
fi

cat <<EOF >| "$COMMIT_MSG_FILE"
Custom commit msg for source=$COMMIT_SOURCE sha1=$SHA1

orig_msg: $orig_msg
git-annex version: `git annex version --raw`
environment:
`export`

EOF

```
</details>

I saw that `git-annex` somehow commits while avoiding this hook entirely!

```
❯ rm random && dd if=/dev/random of=random count=1 && git annex add random && git commit -m "Added random to annex without custom commit msg"; git show git-annex | head -n 5
1+0 records in
1+0 records out
512 bytes copied, 0.000295152 s, 1.7 MB/s
add random 
ok                                
(recording state in git...)
[master 470d6ce] Custom commit msg for source=message sha1=
 1 file changed, 1 insertion(+), 1 deletion(-)
commit 97423356f56f1f16b6a9646614af1d3d4d3d8717
Author: Yaroslav Halchenko <debian@onerussian.com>
Date:   Fri Feb 2 12:03:18 2024 -0500

    update

```

so we got hook working for `master` and commit to `git-annex` branch went without it.  FWIW if I use annex.commitmessage -- that one works but it is inflexible

```shell
❯ rm random && dd if=/dev/random of=random count=1 && git -c annex.commitmessage="custom one" annex add random && git commit -m "Added random to annex WITH custom commit msg"; git show git-annex | head -n 5
1+0 records in
1+0 records out
512 bytes copied, 8.0667e-05 s, 6.3 MB/s
add random 
ok                                
(recording state in git...)
[master 65d4400] Custom commit msg for source=message sha1=
 1 file changed, 1 insertion(+), 1 deletion(-)
commit dff6b4833f4d0e2193d43576c834212f84e54f49
Author: Yaroslav Halchenko <debian@onerussian.com>
Date:   Fri Feb 2 12:05:08 2024 -0500

    custom one
```

I think it would be great if I could just create a "generic" prepare-commit-msg hook I could use for any branch, git-annex included.

The same applies to changes git-annex assistant commits to master -- apparently it seems to avoid that hook as well since even with the hook present I got 

```shell
commit 78c5dcb6bf91b056cba7dc4ee93dd5b31f15f297 (HEAD -> master, synced/master)
Author: Yaroslav Halchenko <debian@onerussian.com>
Date:   Fri Feb 2 12:06:41 2024 -0500

    git-annex in yoh@bilena:~/proj/datalad/trash/try-commit-message
```


[[!meta author=yoh]]
[[!tag projects/repronim]]

> [[done]] --[[Joey]]
