Fix PTY layout problems

[stefanhaller]

• PR Description

This fixes two layout problems with pagers that draw a horizontal line across the entire width of the view (e.g. delta):

• sometimes the width of that line was one character too long or too short in the staged changes view
• when changing from a file or directory that has only staged or only unstaged changes to one that has both, the length of the horizontal line was totally off and only redraw correctly at the next refresh

[codacy-production[bot]]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for c401f345302c96cb77b8c506ac74c6778d937e61[^1]	:white_check_mark: 55.56%

Coverage variation details

| | Coverable lines | Covered lines | Coverage | | ------------- | ------------- | ------------- | ------------- | | Common ancestor commit (c401f345302c96cb77b8c506ac74c6778d937e61) | Report Missing | Report Missing | Report Missing | | | Head commit (8b8343b8a9f81c3000117ce869c734611cf87b7b) | 52286 | 45254 | 86.55% | **Coverage variation** is the difference between the coverage for the head and common ancestor commits of the pull request branch: ` - `

Diff coverage details

| | Coverable lines | Covered lines | Diff coverage | | ------------- | ------------- | ------------- | ------------- | | Pull request (#3658) | 18 | 10 | **55.56%** | **Diff coverage** is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: `/ * 100%`

See your quality gate settings    Change summary preferences

---

_{:rocket: Don’t miss a bit, follow what’s new on Codacy.}

_{Codacy stopped sending the deprecated coverage status on June 5th, 2024. Learn more} [^1]: Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct.