# Plugin – lektor-git-timestamp 1.0.0

Lektor type to deduce page modification time from git

#### Project links

#### Meta

Version: 1.0.0

Author: Jeff Dairiki

#### Tags

git, metadata, and setup-env

View all tags.

## Project Description

# Lektor-Git-Timestamp

This Lektor plugin implements a new datetime-like type, `gittimestamp`, which gets it's default value from git timestamps. This can be used to implement auto-updating `pub_date` and `last_mod` fields in Lektor datamodels.

## Description

The `gittimestamp` type behaves just like the built-in `datetime` type, except that if the field is left blank in `contents.lr` a default value will be deduced from git timestamps for the file (or possibly the file’s filesystem mtime.)

If an explicit value for the field is not found, the git log for the source file (typically `contents.lr`) is searched using `git log --follow --remove-empty -- <source_filename>`, and the author timestamp of all matching commits are considered. Additionally, if the source file is dirty with respect to git’s HEAD, or if the file is not checked into the git tree, the file’s mtime is prepended to that list of timestamps. That list of timestamps is filtered based on the `ignore_commits` and `skip_first_commit` options (see below); then, finally, a timestamp is selected from those that remain based on the setting of the `strategy` option.

### Field Options

The `gittimestamp` type supports the following options.

#### `ignore_commits`

This can be set to a string, which is interpreted as a regular expression. Any git commits whose commit message matches this pattern are ignored when computing a default timestamp value for the field. (The matching is performed using `re.search`.)

#### `skip_first_commit`

If this boolean option is set, the first commit in the git log for the source file will be ignored. This is useful for implementing a `last_mod` field which has a defined value only if the source file has actually been modified since the initial commit.

#### `strategy`

This option determines which timestamp is selected from the git log (and/or the file mtime). This can be set to one of four values:

- `last`: If the source file is dirty (with respect to the git HEAD tree), the mtime of the file is used. Otherwise, the timestamp of the last (nominally the most recent) non-ignored git commit is used. This is the default strategy.

- `first`: The timestamp of the first (nominally the earliest) commit is used.

- `latest`: The latest timestamp is used. Normally this produces the same result at `last`, however due to rebasing, cherry-picking, etc. the git timestamps may not be monotonically increasing, in which case this option causes the greatest (most recent) timestamp remaining after any filtering to be selected.

- `earliest`: The earliest timestamp is used. Normally this produces the same result at `first`, but if the timestamps in the git log are not monotonic, this will select the minimum of all the timestamps remaining after any filtering.

### Global Configuration

The following global configuration options are supported. These values are specified by way of the plugins' configuration file: `configs/git-timestamp.ini` under the project site directory.

By default, the `--follow` option is passed to `git log` when computing timestamps. This behavior may be adjusted on a global basis by way of the plugins' configuration file (`configs/git-timestamp.ini` under the project site directory) via the following settings:

#### `follow_renames`

This is a boolean setting that specifies whether the `--follow` option should be passed to `git log` when querying git for timestamps. This options causes `git` to attempt to follow file renames.

Currently, the `follow_renames` is not supported when Lektor Alternatives are enabled.

If unspecified, `follow_renames` defaults to false.

> Changed in version 1.0.0b3: The default value for `follow_renames` was changed from true to false.

> Note Since we currently run `git log` on a per-record basis, when `--follow` is specified, copied files may be detected as “renamed”. This may not be ideal.

#### `follow_rename_threshold`

Set the similarity index threshold (passed to `git log` via its `-M` option) used when detecting renames. This should be specified as a (floating point) number between 0 and 100, inclusive. Setting `follow_rename_threshold = 100` will limit detection to exact renames only. The default value is 50.

## Examples

Here is a simple example excerpt from a datamodel file:

    <...>

    [fields.last_mod]
    label = Time last modified
    type = gittimestamp

On a page using the above datamodel, so long as the `last_mod` field is left blank in the `contents.lr` file, the page modification time will be deduced from timestamp of the most recent git commit which affected that `contents.lr`. (Or if that file is dirty, the value of `last_mod` will be taken from the file’s filesystem mtime.)

Here is a more complicated example which demonstrates the use of all the options.

    <...>

    [fields.pub_date]
    label = Time first published
    type = gittimestamp
    strategy = first

    [fields.last_mod]
    label = Time last modified
    type = gittimestamp
    ignore_commits = \[nochange\]
    skip_first_commit = true

This will get the default value of the `pub_date` field from the timestamp of the first (earliest) git commit for the source file.

The default value for `last_mod` will, as in the previous example, be taken from the most recent commit for the file, except that:

- any commits whose commit message include the tag `[nochange]` will be ignored
- the first commit (the one whose timestamp is used for `pub_date`) is ignored

If there has only been one commit of the source file, `last_mod` will not have a default value. (It will evaluate to a jinja2 Undefined instance.)

## Warning: On sorting by `gittimestamp` in `Lektor < 3.3`

A common use case for timestamps is for sorting records. E.g. in a blog one generally wants to display posts in reverse chronological order by post date. This generally won't work using `gittimestamp` timestamps with version of Lektor before 3.3.

The `gittimestamp` type is implemented using a field descriptor. (This is required in order to defer computation of the field value until after the record for the page is available.) In `lektor<3.3`, field descriptors are supported for most usages, the one glaring exception being when sorting records.

This was fixed in Lektor PR #789 which was merged to the master branch on February 6, 2021, but didn't make it into a release until Lektor 3.3, released on December 13 2021.

## Author

Jeff Dairiki dairiki@dairiki.org

## Changelog

### Release 1.0.0 (2024-02-06)

No code changes from 1.0.0b3

### Release 1.0.0b3 (2024-01-23)

#### Breaking Changes

- Drop support for python 3.8.
- The default value for the `follow_renames` global config setting has changed from true to false.

#### Bugs Fixed

- Fix to work when alternatives are enabled. Note that in this case the `follow_renames` global option is not supported.

#### Testing

- Test under python 3.12.

#### Code Style

- Style: Use ruff for style linting and formatting. This replaces our usage of `black`, `reorder-python-imports`, and `flake8`.

### Release 1.0.0b2 (2023-06-15)

- Added type annotations.
- Convert packaging to PDM.

#### Code Style

- Style: Run black and reorder-python-imports on code. Configure pre-commit to keep all up-to-date.

#### Tests

- Disuse the deprecated module `pkg_resources`.

#### Buglets

- Do not strip trailing whitespace from `git log` output. (This was erroneously removing trailing newlines from the final commit message.)

### Release 1.0.0b1 (2023-04-11)

- Drop support for python 2.7 and 3.6. (#2)

#### Testing

- Test under python 3.10 and 3.11. (#2)

- Test that `lektor.db.Record.get_sort_key` works with descriptor-valued fields. (This requires `lektor>=3.3`.)

### Release 0.1.0.post1 (2021-08-12)

No code changes.

Add warning to README about `lektor > 3.2` (not yet released) being required in order to be able to sort records by `gittimestamp` fields.

### Release 0.1 (2021-02-05)

No code changes.

Update development status classifier to "stable".

Add functional tests.

### Release 0.1a2 (2021-02-03)

#### Bugs Fixed

Fixed attrocious typo which prevented the use of anything other than the default `strategy=last` for picking timestamps.

### Release 0.1a1 (2020-06-16)

Initial release.

## Comments