docs: document .juliabundleignore in more detail (#105)

Author: mortenpi

docs/src/reference/job-submission.md

@@ -126,6 +126,30 @@ Batch jobs are Julia scripts with (optional) associated Julia package environmen
 
 See also: [`@script_str`](@ref), [`script`](@ref), [`appbundle`](@ref) for more details, and the [guide on submitting batch jobs](@ref jobs-guide-batch) for a tutorial.
 
+### [`.juliabundleignore` file](@id jobs-batch-juliabundleignore)
+
+A `.juliabundleignore` file can be use to exclude certain files from the appbundle that gets submitted to JuliaHub.
+This is useful if you have some temporary development or data files in your project directory, in particular if they are large.
+
+Generally, the file is similar to a `.gitignore` file (though not as feature rich), containing a list of [glob](https://en.wikipedia.org/wiki/Glob_(programming)) patterns.
+More precisely, it uses [Glob.jl](https://github.com/vtjnash/Glob.jl) to match the patterns in the file against file system paths.
+
+For example, a valid `.juliabundleignore` might contain the following entries to exclude a particular directory and all CSV files:
+
+```
+output.log
+*.csv
+output-data/
+```
+
+This `.juliabundleignore` will ignore:
+
+- The `output.log` file next to the `.juliabundleignore`.
+- All `.csv` files next to the `.juliabundleignore` and in subdirectories.
+- All the contents of the `output-data/` directory next to the `.juliabundleignore`.
+
+You can also have additional `.juliabundleignore` files in subdirectories and they will only apply to those directories and their subdirectories.
+
 ### Specifying the job image
 
 JuliaHub batch jobs can run in various container images.

src/jobsubmission.jl

@@ -738,6 +738,9 @@ The following should be kept in mind about how appbundles are handled:
   Registered packages are installed via the package manager via the standard environment
   instantiation, and their source code is not included in the bundle directly.
 
+* You can use `.juliabundleignore` files to omit some files from the appbundle (secrets, large data files etc).
+  See the [relevant section in the reference manual](@ref jobs-batch-juliabundleignore) for more details.
+
 * When the JuliaHub job starts, the bundle is unpacked and the job's starting working directory
   is set to the root of the unpacked appbundle directory, and you can e.g. load the data from those
   files with just `read("my-data.txt", String)`.

test/fixtures/bundle1/Manifest.toml

@@ -0,0 +1,7 @@
+# This file is machine-generated - editing it directly is not advised
+
+julia_version = "1.12.0-rc1"
+manifest_format = "2.0"
+project_hash = "71853c6197a6a7f222db0f1978c7cb232b87c5ee"
+
+[deps]

test/fixtures/bundle1/Project.toml

@@ -0,0 +1 @@
+[deps]