82 lines
2.7 KiB
Markdown
82 lines
2.7 KiB
Markdown
# lethe README
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```lethe``` is a Python module for git-based snapshotting.
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```lethe``` is intended as a mechanism for creating commits outside
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the standard git branching/tagging workflows. It is meant to enable
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additional use-cases without disrupting the standard workflows.
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Use cases include:
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- Short-lived:
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- On-disk **undo log**
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- **Syncing work-in-progress** between computers before it's ready
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- Long-lived:
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- **lab notebook**: Recording the code / configuration state that resulted in a given output
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- **incremental backup**: Space-efficient time-based backups of a codebase
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## Usage
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### Creating a commit from the command line
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```bash
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$ cd path/to/repo
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$ lethe
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122d058e375274a186c407f28602c3b14a2cab95
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```
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This effectively snapshots the current state of the repository (as would be seen by
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```git add --all```) and creates a new commit (```122d058e375274a186c407f28602c3b14a2cab95```)
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which points to it. The current branch and index are not changed.
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### Flags:
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- ```-p my_parent_ref``` is used to provide "parent" refs which become the parents of the created commit.
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If a parent ref is a symbolic ref, *both* the provided ref and the ref it points to are used as parents.
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If not present, defaults to ```-p HEAD```.
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- ```-t ref/lethe/my_target_ref``` is used to provide "target" refs which will be created/updated
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to point to the created commit.
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If not present, defaults to adding an entry of the form ```-t refs/lethe/my_branch``` for each
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parent ref of the form ```refs/heads/my_branch```, and ```-t refs/lethe/my/refpath``` for non-head
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refs of the form ```refs/my/refpath```. All provided parent refs *and* any dereferenced parent refs
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are used to generate default target refs.
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If any of the target refs already exist, the commits they point to become parents of the created commit.
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- ```-m "my message"``` sets the commit message for the snapshot. By default, "snapshot <current datetime>" is used.
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- ```-r path/to/repo``` can be provided to specify a repository outside of the current working directory.
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```bash
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$ cd path/to/repo
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$ git branch
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* master
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$ lethe
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```
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is equivalent to
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```bash
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lethe -r path/to/repo -p HEAD
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```
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or
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```bash
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lethe -r path/to/repo -p HEAD -p refs/heads/master -t refs/lethe/HEAD -t refs/lethe/master
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```
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### Creating a commit programmatically
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```python
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import lethe
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REPO = '/path/to/repo'
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commit_sha = lethe.snap(cwd=REPO)
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tree_sha = lethe.get_tree(commit_sha, cwd=REPO)
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print('Created new commit with hash ' + commit_sha + ' aka refs/lethe/HEAD')
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print('Code (tree) state is ' + tree_sha)
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```
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## Installation
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Requirements:
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* python 3 (written and tested with 3.6)
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* git (accessible on the system ```PATH```)
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Install with pip:
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```bash
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pip install lethe
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```
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