Fix: Make end date inclusive for all activities (issues, commits, PRs)

[Copilot]

Problem

Activities created on the selected end date were not appearing in the analysis results. For example, issues posted on October 3rd would not appear unless October 4th was selected as the end date, making the date picker behavior unintuitive and inconsistent with user expectations.

Root Cause

While the frontend correctly sends the end date with time set to 23:59:59.999 to include the entire day, the backend was converting this to date-only strings (e.g., "2024-10-03") for GitHub GraphQL queries. GitHub's API interprets date-only strings as the start of that day (00:00:00), which excluded any activities created after midnight on the end date.

Before this fix:

User selects: Oct 1 - Oct 3
Backend sends: created:<=2024-10-03
GitHub interprets: created:<=2024-10-03T00:00:00Z
Result: Only items created at exactly midnight are included ❌

Solution

Add 1 day to the until date when constructing GitHub API queries. Since GitHub's until parameter and date comparisons are exclusive (or use start-of-day for date strings), adding 1 day makes the original end date fully inclusive.

After this fix:

User selects: Oct 1 - Oct 3
Backend sends: created:<2024-10-04
GitHub interprets: created:<2024-10-04T00:00:00Z
Result: All items created during Oct 3 are included ✅

Changes

Modified src/services/github.ts with minimal, surgical changes to three methods:

1. getIssuesSince() - Added 1 day to the until date when creating the date-only ISO string for GraphQL search, and changed the search operator from <= to <
2. fetchCommitsForDefaultBranch() - Added 1 day to the until timestamp parameter
3. getCommitCountsAcrossBranches() - Added 1 day to the until timestamp parameter

Note: getPullRequestsSince() was already working correctly because it uses timestamp comparison which preserves the time component.

Testing

Validated the fix with multiple scenarios:

• ✅ Items created on the end date at any time (midnight, afternoon, end of day) are now included
• ✅ Items created after the end date (next day at midnight) are correctly excluded
• ✅ Single-day date ranges (start date = end date) work correctly
• ✅ All existing linting and build checks pass

Impact

This fix resolves the unintuitive behavior where users had to select the next day to see activities from their desired end date. The end date picker now works as expected, including all activities that occurred during the selected day.

Stats: 16 insertions(+), 4 deletions(-) in 1 file

Original prompt

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This section details on the original issue you should resolve

<issue_title>End date of period should be inclusive</issue_title>
<issue_description>Issues posted on October 3rd will not appear in the table unless October 4th is selected as the end date of the period.
This behavior isn't really intuitive or desirable.
Instead, we should include all activity up to and including the specified end date.
This probably affects everything that we look at (not just issues).

</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #25

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