Bash completion for `gtr` wrapper breaks with 2+ character input

[zhfeng]

Bug Description

Bash tab completion for the gtr wrapper function (generated by git gtr init bash) fails when the user has typed 2 or more characters of the completion target. It works correctly with git gtr.

Example (given branches: main, feature/login, fix/typo):

• gtr ai f<TAB> → works (1-char input, shows feature/login and fix/typo)
• gtr ai fe<TAB> → nothing (2-char input, should show feature/login)
• gtr ai ma<TAB> → wrong result (returns a different branch instead of main)
• git gtr ai fe<TAB> → works correctly in all cases

Root Cause

The _gtr_completion function (output of git gtr init bash) updates COMP_WORDS and COMP_CWORD when delegating to _git_gtr, but does not update COMP_LINE and COMP_POINT:

# Current code in _gtr_completion (delegation branch):
COMP_WORDS=(git gtr "${COMP_WORDS[@]:1}")
(( COMP_CWORD += 1 ))
_git_gtr

The bash-completion v2 function _init_completion → _comp_get_words → _comp__get_cword_at_cursor re-parses COMP_LINE (not COMP_WORDS) to determine the current word (cur). Because COMP_LINE still contains "gtr ai fe" while COMP_WORDS has been changed to (git gtr ai fe), the word-boundary matching in _comp__get_cword_at_cursor fails — it tries to match words[0]="git" against a COMP_LINE starting with "gtr", corrupting the cur variable.

With single-character inputs it happens to work by coincidence (the misaligned parsing still lands on the right character), but with 2+ characters the misalignment causes cur to be wrong or empty.

Proposed Fix

Update COMP_LINE and COMP_POINT alongside COMP_WORDS and COMP_CWORD in the delegation branches of _gtr_completion. Replace "gtr " (4 chars) with "git gtr " (8 chars) in COMP_LINE, and shift COMP_POINT by 4:

COMP_WORDS=(git gtr "${COMP_WORDS[@]:1}")
(( COMP_CWORD += 1 ))
COMP_LINE="git gtr ${COMP_LINE#gtr }"
(( COMP_POINT += 4 ))
_git_gtr

This needs to be applied in both delegation sites within _gtr_completion — the new branch and the general fallback branch.

Verification

Simulated completion calls before and after the fix (given branches: main, feature/login, fix/typo):

Before (broken):

gtr ai ""    => 4 matches (ok)
gtr ai "f"   => 2 matches (ok - by coincidence)
gtr ai "fe"  => 0 matches (WRONG - should be 1)
gtr ai "fi"  => 0 matches (WRONG - should be 1)
gtr ai "ma"  => wrong branch returned (WRONG - should be "main")

After (fixed):

gtr ai ""    => 4 matches (ok)
gtr ai "f"   => 2 matches (ok)
gtr ai "fe"  => 1 match: feature/login (ok)
gtr ai "fi"  => 1 match: fix/typo (ok)
gtr ai "ma"  => 1 match: main (ok)

Environment

• macOS (Darwin)
• git-gtr 2.5.0 (Homebrew)
• bash 5.x (Homebrew) with bash-completion@2