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Tree supports the -I flag.

-I pattern
   Do not list those files that match the wild-card pattern.

Tree supports a single pattern which will exclude all files/directories that match it.

Git's ignore files are a bit more complicated:

Exclusion can come from multiple files, $HOME/.config/git/ignore, the output of git config --get core.excludesfile , .gitignore (per directory), ~/.gitignore, and more (see man gitignore).

Another problem is the patterns that tree supports differs from what git does (as noted by @Brad Urani).

But we can get close-ish ...

tree -I "$(grep -hvE '^$|^#' {~/,,$(git rev-parse --show-toplevel)/}.gitignore|sed 's:/$::'|tr \\n '\|')"

Or as a function:

function gtree {
    git_ignore_files=("$(git config --get core.excludesfile)" .gitignore ~/.gitignore)
    ignore_pattern="$(grep -hvE '^$|^#' "${git_ignore_files[@]}" 2>/dev/null|sed 's:/$::'|tr '\n' '\|')"
    if git status &> /dev/null && [[ -n "${ignore_pattern}" ]]; then
      tree -I "${ignore_pattern}" "${@}"
    else 
      tree "${@}"
    fi
}

Tree supports the -I flag.

-I pattern

Do not list those files that match the wild-card pattern.

Tree supports a single pattern which will exclude all files/directories that match it.

Git's ignore files are a bit more complicated:

Exclusion can come from multiple files, $HOME/.config/git/ignore, the output of git config --get core.excludesfile , .gitignore (per directory), ~/.gitignore, and more (see man gitignore).

Another problem is the patterns that tree supports differs from what git does (as noted by @Brad Urani).

But we can get close-ish ...

tree -I "$(grep -hvE '^$|^#' {~/,,$(git rev-parse --show-toplevel)/}.gitignore|sed 's:/$::'|tr \\n '\|')"

Or as a function:

function gtree {
    git_ignore_files=("$(git config --get core.excludesfile)" .gitignore ~/.gitignore)
    ignore_pattern="$(grep -hvE '^$|^#' "${git_ignore_files[@]}" 2>/dev/null|sed 's:/$::'|tr '\n' '\|')"
    if git status &> /dev/null && [[ -n "${ignore_pattern}" ]]; then
      tree -I "${ignore_pattern}" "${@}"
    else 
      tree "${@}"
    fi
}

Tree supports the -I flag.

-I pattern
   Do not list those files that match the wild-card pattern.

Tree supports a single pattern which will exclude all files/directories that match it.

Git's ignore files don't work like this. Exclusion come from multiple files: $HOME/.config/git/ignore, the output of git config --get core.excludesfile , .gitignore (per directory), ~/.gitignore, and more (see man gitignore). The per directory ignore files only ignore files starting from that directory. Tree doesn't support this.

The other problem is we have is the patterns that patterns that tree supports is differs from what git does. (as noted by @Brad Urani) But we can get close-ish ...

tree -I "$(grep -hvE '^$|^#' {~/,,$(git rev-parse --show-toplevel)/}.gitignore|tr \\n '\|')"

Or as a function:

function gtree {
    git_ignore_files=("$(git config --get core.excludesfile)" .gitignore ~/.gitignore)
    ignore_pattern="$(grep -hvE '^$|^#' "${git_ignore_files[@]}" 2>/dev/null|tr '\n' '\|')"
    if git status &> /dev/null && [[ -n "${ignore_pattern}" ]]; then
      tree -I "${ignore_pattern}" "${@}"
    else 
      tree "${@}"
    fi
}

Tree supports the -I flag.

-I pattern
   Do not list those files that match the wild-card pattern.

Tree supports a single pattern which will exclude all files/directories that match it.

Git's ignore files are a bit more complicated:

Exclusion can come from multiple files, $HOME/.config/git/ignore, the output of git config --get core.excludesfile , .gitignore (per directory), ~/.gitignore, and more (see man gitignore).

Another problem is the patterns that tree supports differs from what git does (as noted by @Brad Urani).

But we can get close-ish ...

tree -I "$(grep -hvE '^$|^#' {~/,,$(git rev-parse --show-toplevel)/}.gitignore|sed 's:/$::'|tr \\n '\|')"

Or as a function:

function gtree {
    git_ignore_files=("$(git config --get core.excludesfile)" .gitignore ~/.gitignore)
    ignore_pattern="$(grep -hvE '^$|^#' "${git_ignore_files[@]}" 2>/dev/null|sed 's:/$::'|tr '\n' '\|')"
    if git status &> /dev/null && [[ -n "${ignore_pattern}" ]]; then
      tree -I "${ignore_pattern}" "${@}"
    else 
      tree "${@}"
    fi
}

Tree supports the -I flag.

-I pattern
   Do not list those files that match the wild-card pattern.

Tree supports a single pattern which will exclude all files/directories that match it.

Git's ignore files don't work like this. Exclusion come from multiple files: $HOME/.config/git/ignore, the output of git config --get core.excludesfile , .gitignore (per directory), ~/.gitignore, and more (see man gitignore). The per directory ignore files only ignore files starting from that directory. Tree doesn't support this.

The other problem is we have is the patterns that patterns that tree supports is differs from what git does. (as noted by @Brad Urani) But we can get close-ish ...

tree -I "$(grep -hvE '^$|^#' {~/,,$(git rev-parse --show-toplevel)/}.gitignore|tr \\n '\|')"

Or as a function:

function gtree {
    git_ignore_files=("$(git config --get core.excludesfile)" .gitignore ~/.gitignore)
    ignore_pattern="$(grep -hvE '^$|^#' "${git_ignore_files[@]}" 2>/dev/null|tr '\n' '\|')"
    if git status &> /dev/null && [[ -n ${ignore_pattern} ]]; then
      tree -I "${ignore_pattern}" "${@}"
    else 
      tree "${@}"
    fi
}

Tree supports the -I flag.

-I pattern
   Do not list those files that match the wild-card pattern.

Tree supports a single pattern which will exclude all files/directories that match it.

Git's ignore files don't work like this. Exclusion come from multiple files: $HOME/.config/git/ignore, the output of git config --get core.excludesfile , .gitignore (per directory), ~/.gitignore, and more (see man gitignore). The per directory ignore files only ignore files starting from that directory. Tree doesn't support this.

The other problem is we have is the patterns that patterns that tree supports is differs from what git does. (as noted by @Brad Urani) But we can get close-ish ...

tree -I "$(grep -hvE '^$|^#' {~/,,$(git rev-parse --show-toplevel)/}.gitignore|tr \\n '\|')"

Or as a function:

function gtree {
    git_ignore_files=("$(git config --get core.excludesfile)" .gitignore ~/.gitignore)
    ignore_pattern="$(grep -hvE '^$|^#' "${git_ignore_files[@]}" 2>/dev/null|tr '\n' '\|')"
    if git status &> /dev/null && [[ -n "${ignore_pattern}" ]]; then
      tree -I "${ignore_pattern}" "${@}"
    else 
      tree "${@}"
    fi
}