Support {python} placeholder

changelog.d/20231009_185242_michael.hanke_noexe.md

@@ -0,0 +1,9 @@
+### 🚀 Enhancements and New Features
+
+- A new placeholder `{python}` is supported by container execution.
+  It resolves to the Python interpreter executable running DataLad
+  on container execution. This solves portability issues with the
+  previous approach of hard-coding a command name on container
+  configuration.
+  Fixes https://github.com/datalad/datalad-container/issues/226 via
+  https://github.com/datalad/datalad-container/pull/227 (by @mih)

datalad_container/containers_add.py

@@ -65,7 +65,8 @@ def _guess_call_fmt(ds, name, url):
     elif url.startswith('shub://') or url.startswith('docker://'):
         return 'singularity exec {img} {cmd}'
     elif url.startswith('dhub://'):
-        return op.basename(sys.executable) + ' -m datalad_container.adapters.docker run {img} {cmd}'
+        # {python} is replaced with sys.executable on *execute*
+        return '{python} -m datalad_container.adapters.docker run {img} {cmd}'
 
 
 def _ensure_datalad_remote(repo):
@@ -143,6 +144,9 @@ class ContainersAdd(Interface):
             replaced with the desired command. Additional placeholders:
             '{img_dspath}' is relative path to the dataset containing the image,
             '{img_dirpath}' is the directory containing the '{img}'.
+            '{python}' expands to the path of the Python executable that is
+            running the respective DataLad session, for example a
+            'datalad containers-run' command.
             """,
             metavar="FORMAT",
             constraints=EnsureStr() | EnsureNone(),

datalad_container/containers_run.py

@@ -4,6 +4,7 @@
 
 import logging
 import os.path as op
+import sys
 
 from datalad.interface.base import Interface
 from datalad.interface.base import build_doc
@@ -115,6 +116,10 @@ def __call__(cmd, container_name=None, dataset=None,
                         'Convert it to a plain string.'.format(callspec))
             try:
                 cmd_kwargs = dict(
+                    # point to the python installation that runs *this* code
+                    # we know that it would have things like the docker
+                    # adaptor installed with this extension package
+                    python=sys.executable,
                     img=image_path,
                     cmd=cmd,
                     img_dspath=image_dspath,