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skills/get-git-diff/scripts/diff_stats.sh

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+#!/usr/bin/env bash
+#
+# Git Diff Statistics Functions
+#
+# Functions for calculating and analyzing diff statistics.
+#
+# Author: Claude Code get-git-diff skill
+# Version: 1.0.0
+
+set -euo pipefail
+
+#######################################
+# Get diff statistics between two commits
+# Arguments:
+#   $1 - first commit
+#   $2 - second commit
+# Outputs:
+#   Tab-separated: files_changed insertions deletions net_change
+#######################################
+get_diff_stats() {
+    local commit1="$1"
+    local commit2="$2"
+    local shortstat
+
+    if shortstat=$(git diff --shortstat "${commit1}...${commit2}" 2>/dev/null); then
+        local files=0 insertions=0 deletions=0
+
+        # Parse: "3 files changed, 165 insertions(+), 20 deletions(-)"
+        if [[ ${shortstat} =~ ([0-9]+)\ files?\ changed ]]; then
+            files="${BASH_REMATCH[1]}"
+        fi
+        if [[ ${shortstat} =~ ([0-9]+)\ insertions? ]]; then
+            insertions="${BASH_REMATCH[1]}"
+        fi
+        if [[ ${shortstat} =~ ([0-9]+)\ deletions? ]]; then
+            deletions="${BASH_REMATCH[1]}"
+        fi
+
+        local net_change=$((insertions - deletions))
+        echo "${files}	${insertions}	${deletions}	${net_change}"
+    else
+        echo "0	0	0	0"
+    fi
+}
+
+#######################################
+# Get detailed per-file statistics
+# Arguments:
+#   $1 - first commit
+#   $2 - second commit
+# Outputs:
+#   Tab-separated: insertions deletions filename (one per line)
+#######################################
+get_file_stats() {
+    local commit1="$1"
+    local commit2="$2"
+
+    git diff --numstat "${commit1}...${commit2}" 2>/dev/null
+}
+
+#######################################
+# Check if diff is large (exceeds threshold)
+# Arguments:
+#   $1 - first commit
+#   $2 - second commit
+#   $3 - threshold (optional, default: 1000)
+# Returns:
+#   0 if large, 1 if not
+# Outputs:
+#   Total line count if large
+#######################################
+is_large_diff() {
+    local commit1="$1"
+    local commit2="$2"
+    local threshold="${3:-1000}"
+    local stats
+
+    if stats=$(get_diff_stats "${commit1}" "${commit2}"); then
+        local insertions deletions total_lines
+        insertions=$(echo "${stats}" | cut -f2)
+        deletions=$(echo "${stats}" | cut -f3)
+        total_lines=$((insertions + deletions))
+
+        if [[ ${total_lines} -gt ${threshold} ]]; then
+            echo "${total_lines}"
+            return 0
+        fi
+    fi
+
+    return 1
+}
+
+#######################################
+# Get total line count in diff
+# Arguments:
+#   $1 - first commit
+#   $2 - second commit
+# Outputs:
+#   Total lines changed (insertions + deletions)
+#######################################
+get_total_lines() {
+    local commit1="$1"
+    local commit2="$2"
+    local stats
+
+    if stats=$(get_diff_stats "${commit1}" "${commit2}"); then
+        local insertions deletions
+        insertions=$(echo "${stats}" | cut -f2)
+        deletions=$(echo "${stats}" | cut -f3)
+        echo $((insertions + deletions))
+    else
+        echo "0"
+    fi
+}
+
+#######################################
+# Get files changed count
+# Arguments:
+#   $1 - first commit
+#   $2 - second commit
+# Outputs:
+#   Number of files changed
+#######################################
+get_files_changed() {
+    local commit1="$1"
+    local commit2="$2"
+    local stats
+
+    if stats=$(get_diff_stats "${commit1}" "${commit2}"); then
+        echo "${stats}" | cut -f1
+    else
+        echo "0"
+    fi
+}
+
+# Allow script to be sourced or run directly
+if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
+    # Example usage
+    if [[ $# -lt 2 ]]; then
+        echo "Usage: $0 <commit1> <commit2> [threshold]"
+        echo ""
+        echo "Examples:"
+        echo "  $0 HEAD^ HEAD"
+        echo "  $0 main feature-branch 500"
+        exit 1
+    fi
+
+    commit1="$1"
+    commit2="$2"
+    threshold="${3:-1000}"
+
+    echo "=== Diff Statistics: ${commit1} → ${commit2} ==="
+    stats=$(get_diff_stats "${commit1}" "${commit2}")
+    IFS=$'\t' read -r files ins del net <<< "${stats}"
+
+    echo "Files changed: ${files}"
+    echo "Insertions: +${ins}"
+    echo "Deletions: -${del}"
+    echo "Net change: ${net}"
+    echo "Total lines: $((ins + del))"
+
+    if is_large_diff "${commit1}" "${commit2}" "${threshold}"; then
+        total=$(is_large_diff "${commit1}" "${commit2}" "${threshold}")
+        echo "⚠ Large diff detected (${total} lines, threshold: ${threshold})"
+    else
+        echo "✓ Normal size diff (threshold: ${threshold})"
+    fi
+
+    echo ""
+    echo "=== Top 10 Changed Files ==="
+    get_file_stats "${commit1}" "${commit2}" | head -10 | while IFS=$'\t' read -r ins del file; do
+        if [[ "${ins}" == "-" && "${del}" == "-" ]]; then
+            echo "  ${file} (binary)"
+        else
+            echo "  ${file} (+${ins}, -${del})"
+        fi
+    done
+fi